主旨大意题 知识点题库

    The weather is getting hotter. You are thirsty playing basketball or riding home from school. A cold drink may be just the thing. But be careful what you are drinking. Something that looks cool may not be good for your health.

    There are plenty of “energy drinks” on the market. Most of them have beautiful colors and cool names. The lists on them tell you they are helpful to your health. Sounds great!

    But after a careful check you may find that most energy drinks have lots of caffeine(咖啡碱)in them. These drinks are especially aimed at young people, students, busy people and sports players. Makers sometimes say their drinks make you better at sports and can keep you awake. But be careful not to drink too much. Caffeine makes your heart beat fast. Because of this, the International Olympic Committee(IOC) has limited(限制) its use. Caffeine in most energy drinks is at least as strong as that in a cup of coffee or tea.

    Possible health dangers have something to do with energy drinks. Just one box of energy drink can make you nervous, have difficulty sleeping and can even cause heart problems. Scientists say that teenagers should be discouraged from taking drinks with a lot of caffeine in them.

    My roommate Lily was well organized, while I was not. Each of her objects had its place, but mine always hid somewhere. She even labeled (贴标签) everything. I always looked for everything. Over time, Lily got neater and I got messier. She would push my dirty clothing over, and I would lay my books on her tidy desk. We both got tired of each other.

    War broke out one evening. Lily came into the room. Soon, I heard her screaming. “Take your shoes away! Why under my bed!” Deafened, I saw my shoes flying at me. I jumped to my feet and started yelling. She yelled back louder.

    The room was filled with anger. We could not have stayed together for a single minute but for a phone call. Lily answered it. From her end of the conversation, I could tell right away her grandma was seriously ill. When she hung up, she quickly crawled (爬) under her covers, sobbing. Obviously, that was something she should not go through alone. All of a sudden, a warm feeling of sympathy rose up in my heart.

    Slowly, I collected the pencils, took back the books, made my bed, cleaned the socks and swept the floor, even on her side. I got so into my work that I even didn't notice Lily had sat up. She was watching, her tears dried and her expression one of disbelief. Then, she reached out her hands to grasp mine. I looked up into her eyes. She smiled at me, “Thanks.”

    Lily and I stayed roommates for the rest of the year. We didn't always agree, but we learned 高一阅读理解My roommate Lily was well organized while I was the key to living together: giving in, cleaning up and holding on.

    A handsome middle-aged man walked quietly into the café and sat down. Before he ordered, he couldn't help but noticed a group of younger men at the table next to him. It was obvious they were making fun of something about him and it wasn't until he remembered he was wearing a small pink ribbon(丝带) on the lapel of his suit that he became aware of what the joke was all about.

The man pretended not to notice it, but the whisper and laughter began to get to him. He looked one of the rude young men straight into the eye, placed his hand beneath the ribbon and asked, “This?”

    With that the young men all began to laugh out loud. The man he spoke to said, “Hey, sorry, man, but we were just commenting on how pretty your little pink ribbon looks against your blue jacket!”

    The middle-aged man calmly invited the joker to come over to his table, and politely seated him. As uncomfortable as he was, the young guy had to, not really sure why. In a soft voice, the middle-aged man said, “I wear this ribbon to bring awareness about breast cancer. I wear it in my mother's honor.”

    “Oh, sorry. She died of breast cancer?”

    “No, she didn't. She's alive and well. But her breasts nourished me as a baby, and were a soft resting place for my head when I was scared or lonely as a little boy. I'm very grateful for my mother's breasts, and her health.”

    “Umm,” the young replied, “yeah.”

    “And I wear this ribbon to honor my wife,” the man continued.

    “And she's okay, too?” the young guy asked.

    “Oh, yes. She's fine. Her breasts have been a great source of loving pleasure for both of us, and with them she nurtured and nourished our daughter 23 years ago. I'm grateful for my wife's breasts, and her health.”

    “Uh, huh. And I guess you wear it to honor your daughter, also?”

    “No. It's too late to honor my daughter by wearing it now ……”

    Shaken and ashamed, the young guy said, “Oh, I'm so sorry, mister.”

    “So, in my daughter's memory, too, I proudly wear this little ribbon, which allows me the opportunity to enlighten others. And here…” With this, he reached in his pocket and handed the young man a little pink ribbon. The young guy looked at it, slowly raised his head and asked, “……?”

    Reading can be a social activity. Think of the people who belong to book groups. They choose books to read and then meet to discuss them. Now, the website BookCrossing.com turns the page on the traditional idea of a book group.

    Members go on the site and register the books they own and would like to share. BookCrossing provides an identification number to stick inside the book. Then the person leaves it in a public place, hoping that the book will have an adventure, traveling far and wide with each new reader who finds it.

    Bruce Pederson, the managing director of BookCrossing, says, “The two things that change your life are the people you meet and books you read. BookCrossing combines both.”

    Members leave books on park benches and buses, in train stations and coffee shops. Whoever finds their book will go to the site and record where they found it.

    People who find a book can also leave a journal entry describing what they thought of it. E-mails are then sent to the BookCrossing to keep them updated about where their books have been found. Bruce Pederson says the idea is for people not to be selfish by keeping a book to gather dust on a shelf at home.

    BookCrossing is part of a trend among people who want to get back to the “real” and not the virtual（虚拟）. The site now has more than one million members in more than one hundred thirty-five countries.

    Five million people visit Grand Canyon in the US every year. For the purpose of helping project Grand Canyon for your fellow visitors and future generations, please follow the guidelines below.

   Camping

    To project the park, camping is allowed only within permitted campgrounds. Permits are required for overnight camping at the North Rim. Advance booking can be received by mail. Please write: Information Center, P.O. Box 129, Grand Canyon, AZ 86023

    Fires

    Because of the extreme fire danger, campfires are not allowed except at Mather and Desert View campgrounds. Collection of firewood is not allowed either.

    Hiking

    Please stay on permitted paths. Otherwise you may destroy desert plants. Pack out what you pack in, so you leave no signs of your visit. It is important to keep in mind that you are in a national park where wildlife exists.

    Weather

    The weather at Grand Canyon can change very quickly. With so much rock, lightning causes a particular danger during sudden summer storms. These storms also frequently bring floods inside valleys, a danger to hikers. Watch the skies and check daily weather reports.

    Wildlife

    Do not feed park wildlife. There have been a few cases at Grand Canyon National Park where deer were purposely shot because they ate plastic bags that left them sick and weak. Hungry deer can be danger and have kicked and bitten visitors at Grand Canyon. Some other animals will also beg and bite. For your own safety and the well-being of the animals, please do not feed wildlife, no matter how gentle they may appear.

    An exciting landing process of Chang'e-4 lunar probe (月球探测器 ) was seen through the monitor at Beijing Aerospace Control Center in Beijing, Jan. 3, 2019. It touched down on the far side of the moon at 10:26 a.m. Beijing Time, becoming the first spacecraft soft-landing on the moon's unknown side never visible from Earth.

    China's Chang'e-4 probe has started the exploration on the far side of the moon thanks to the relay satellite that provides a communication link with ground control. The relay satellite, named Queqiao, meaning Magpie Bridge, after a Chinese legend (传说) , was launched on May 21, 2018, and became the first communication satellite operating in the halo orbit, nearly 500,000 km from the earth. It can also provide communication for probes from other countries. The relay satellite will also be used for scientific and technological experiments. The maximum distance between the satellite and the Chang'e-4 probe on the far side of the moon is 79,000 km. The satellite processes data from the probe and sends it to Earth.

    The satellite can stay in its orbit for a long time due to its relatively low fuel consumption, as the earth's and moon's gravity balances its orbital moving. While in orbit, it can "see" both the earth and the far side of the moon.

    The concept of using a relay satellite in the halo orbit was first put forward by U.S. space experts in the 1960s, but was realized by Chinese space engineers.

    Researchers hope to use the cameras on the satellite to record asteroids (小行星 ) hitting the far side of the moon. To control the cost of the Chang'e-4 probe, the relay satellite was designed to be relatively small, weighing about 400 kg.

    Researchers had just 30 months to develop the satellite, putting them under high pressure. To promote public interest in space exploration, the China National Space Administration invited people to write down their wishes for lunar and space exploration, and the relay satellite carries the names of tens of thousands of participants and their messages.

    My First Marathon

    Three weeks before my first marathon, one of my ankles was injured and this meant not running for two weeks, leaving me only one week to train. Yet, I was determined to go ahead.

    I remember back to my 7th year in school. In my first P.E. class, the teacher required us to run laps and then hit a softball. My performance was really terrible. He later informed me that I was "not athletic".

    The idea that I was "not athletic" stuck with me for years. When I started running in my 30s, I realized running was a battle against myself, not about competition or whether or not I was athletic. It was all about the battle against my own body and mind. A test of wills!

    The night before my marathon, I dreamt that I couldn't even find the finish line. I woke up sweating and nervous, but I was ready to prove something to myself.

Shortly after crossing the start line, my shoe laces became untied. So I stopped to readjust. Not the start I wanted!

    At mile 3, I passed a sign: "GO FOR IT, RUNNERS!"

    By mile 17, I became out of breath and the once injured ankle hurt badly. Despite the pain, I stayed the course walking a bit and then running again.

    By mile 21, I was starving!

    As I approached mile 23, I could see my wife waving a sign. She is my biggest fan. She never minded the alarm clock sounding at 4 a.m. or questioned my expenses on running.

    I was one of the final runners to finish. But I finished! And I got a medal. In fact, I got the same medal as the one that the guy who came in first place had.

Determined to be myself and move forward, free of shame and worldly labels(世俗标签), I can now call myself a "marathon winner".

    There is an English saying that says, "Let Sleeping Dogs Lie." It means not bringing up an old problem. Researchers in Hungary have found another reason to let dogs keep on sleeping. It seems the animals are learning while they sleep.

    The Hungarian researchers placed tools on the dogs' heads to know about electrical activity in the brain. The brain activity, called sleep spindles(梭状波), takes place in human begins, and has been connected with learning. The researchers hope to understand how the dogs' ability to learn and remember changes as they get older. The study may help them understand how human brains change as we age.

    The researchers found differences between male and female dogs. Iotchey, a researcher, says the females appeared much better at learning new things. Female dogs have about twice as many spindles per minute as male dogs, they also happen to be the better learners, and they memorize the task much better. But it was harder for all the older dogs to remember things, especially when several things were happening at the same time.

    DoraSzabo also studies sleep spindles. Szabo is a neuroscientist in a university in Budapest. She says the older dogs have fewer spindles and are easily cheated. "If you first hide the reward into one bowl, then in another and in another, they get lost after a while. So their performance is going down, and they are getting poor in solving new problems."

    Researchers hope the study will not only help understanding of learning ability and memory changes in dogs, but also the aging of humans. Senior Researcher EnikoKubinyi adds that the aging dogs suffer from the same problems as humans who are aging. “Among very old dogs, up to two thirds of them show signs of dementia(痴呆), and this dementia is really very similar to that of humans, so we could use dog as a natural model of human aging."

    Many people have long dreamed of being able to fly around as simply as riding a bicycle. Yet the safety and strength of a flying bike was always a big problem. Over the past 10 years, developments in technology have moved the dream of personal flying vehicles closer to reality. Now, two groups of inventors say such vehicles may be available soon.

    The British company Malloy Aeronautics has developed a prototype (原型) of its flying bicycle. Grant Stapleton, marketing sales director of Malloy Aeronautics, says the Hoverbike is able to get in and out of small spaces very quickly." It can be moved across continents very quickly because it can be folded and packed," he adds.

    Mr. Stapleton says safety was the company's main concern. He says the designers solved the safety issue by using overlapping rotors to power the vehicle.

    The company is testing a full-size prototype of the Hoverbike, which will most likely be used first by the police and emergency rescue teams.

    In New Zealand, Martin Aircraft Company is also testing a full-size prototype of its personal flying device, called the Jetpack. It can fly for more than 30 minutes, up to 1, 000 meters high and reach a speed of 74 kilometers per hour.

    Peter Coker is the CEO of Martin Aircraft Company. He said the Jetpack "is built around safety from the start". In his words, "Reliability is the most important element of it. We have safety built into the actual structure itself, very similar to a Formula One racing car.

    The Jetpack uses a gasoline-powered engine that produces two powerful jet streams. Mr. Coker says it also has a parachute that would be used, if there should be an emergency. "It starts to work at very low altitude and actually saves both the aircraft and the pilot," he adds. Mr. Coker says the Jetpack will be ready for sale soon.

    If a family member blames you for something you have done, it is important to be careful about how you defend yourself. It is not a good idea to use ways that cause hurt, even if they would help you make a valid point. If you can think of an instance where the other person has done exactly what they accuse you of, for example, it would not be good manners to throw it in their face. You should only bring it up if you don't have a choice. Then, you should make sure that you do it respectfully.

    Even if a family member intentionally goes against reasonable wishes you may have, you should understand that people see even the most fundamental things in very different ways. Remember that people are different. If you consider any noise after midnight to be intolerable, for example, others may see it is completely acceptable. It can take them a great deal of time to change their behavior for a demand that they do not understand.

    Think about the family conflicts that you are worried about now. Check to see if your parents had similar problems. People who grow up with parents who fight unfairly often repeat the same behavior. Consider changing the unfair habits that you grew up with.

    Understand that memories tend to change. In long-standing family disputes, all parties involved tend to have completely different recollections of the original problem.

    Families are a curious concept—while family members often feel nothing but annoyed for one another, they will also often be there for them if they should ever be in serious trouble. When you feel resentment for someone, think about how far you would go for them if they happened to be in trouble. It could help soften you. Think about how you care for the other person.

    Western conservation groups are seeking stricter laws to deal with trade in endangered wildlife, but Dr. Paul Jepson warns that this isn't the best solution. He highlights the case of the Bali starling (八哥). Bringing in tougher laws created unexpected outcomes, which contributed to the bird's extinction in the wild in 2006.

    He said that the traditional law enforcement (执行) approach that outlawed (宣布……非法) ownership of the Bali starling in the 1980s and 1990s increased rather than reduced the demand for wild-caught Bali starlings. The bird has become a popular gift among the rich of Indonesia, who can gain more status by owning one.

    Instead, a case-by-case analysis might be needed. Last year, he said, a bird association set up a network of breeders (饲养者) among the owners of Bali starling on the island of Java. By introducing a "crowd-breeding" model, it transformed the bird into a species whose price and source of supply were publicly known. This lessened the status of keeping such birds and thereby reduced their profitability to black market suppliers.

    Another case was on Nusa Penida, an island southeast of Bali. A Balinese conservation group planned to release starlings on the island. Critics tried to block the plan, saying the island was outside the birds' native zone. Eventually, the Governor of Bali came up with a proposal. The starlings were given to a local temple as a ceremonial offering before they were released. This gave the Bali starling status as a "sacred bird", giving them protection under customary laws. Now the released starlings established a breeding population on Nusa Penida.

    Dr. Jepson commented, "I do not want to criticize the international approach seeking tighter law enforcement, but this case study shows we should not oversimplify how we respond to the problem of the wildlife trade. There is a growing body of evidence that shows more different approaches are sometimes needed to fit with the local social and political realities. We should tailor solutions on more of a case-by-case basis."

    Music is an international language. The songs that are sung or played by instruments are beautiful to all people everywhere.

    Popular music in America is what every student likes. Students carry small radios with earphones and listen to music before class, after class and at lunch. Students with cars buy large speakers(扬声器)and play the music loudly as they drive on the street.

    Adult drivers listen to music on the car radio as they drive to work. They also listen to the news about sports, the weather, politics, and activities of the American people. But most of the radio broadcast is music.

    Pop or popular music singers make much money. They make a CD or tape which radio stations use in every state. Once the popular singer is heard throughout the country, young people buy his or her tapes. Some of the money from these tapes comes to the singer. Wherever the singer goes, all the young people want to meet him or her. Now the singer has become a national star.

    Besides pop music, there are two other kinds of music that is important to Americans. One is called folk music. It tells stories about the common life of Americans. The other is called western or country music. This was started by cowboys who would sing at night to the cows they were watching. Today, any music about country life and the love between a country boy and his girl is called western or country music.

    Serious music for the concert halls is called classical music. Music for instruments is called orchestra music, such as the symphonies(交响乐)of Beethoven. There is opera for singers, ballet for dancers like the story of Liang Shanbo and Zhu Yingtai in China.

    PITTSBURGH — For most people, snakes seem unpleasant or even threatening. But Howie Choset sees in their delicate movements a way to save lives.

    The 37-year-old Carnegie Mellon University professor has spent years developing snake-like robots he hopes will eventually slide through fallen buildings in search of victims trapped after natural disasters or other emergencies.

    Dan Kara is president of Robotics Trends, a Northboro, mass-based company that publishes an online industry magazine and runs robotics trade shows. He said there are other snake-like robots being developed, mainly at universities, but didn't know of one that could climb pipes.

    The Carnegie Mellon machines are designed to carry cameras and electronic sensors and can be controlled with a joystick (操纵杆). They move smoothly with the help of small electric motors, or servos, commonly used by hobbyists in model airplanes.

    Built from lightweight materials, the robots are about the size of a human arm or smaller. They can sense which way is up, but are only as good as their human operators, Choset added.

    Sam Stover, a search term manager with the Federal Emergency Management Agency based in Indiana, said snake-type robots would offer greater mobility than equipment currently available, such as cameras attached to extendable roles.

    "It just allows us to do something we've not been able to do before," Stover said, "We needed them yesterday."

    He said sniffer dogs are still the best search tool for rescue workers, but that they can only be used effectively when workers have access to damaged building.

    Stover, among the rescue workers who handled the aftermath (后果) of Hurricane Katrina, said snake robots would have helped rescuers search flooded houses in that disaster.

    Choset said the robots may not be ready for use for another five to ten years, depending on funding.

Astronomers have taken the first ever image of a black hole, which is located in a distant galaxy (星系). The black hole is 500 million trillion km away and was photographed by a network of eight telescopes across the world. It was captured by the Event Horizon Telescope (EHT).

The announcement was made in Washington, Brussels, Santiago, Shanghai, Taipei and Tokyo. Details have been published today in Astrophysical Journal Letters.

Prof Heino Falcke, of Radboud University in the Netherlands, who suggested the experiment, told BBC News that the black hole was found in a galaxy called M87. "What we see is larger than the size of our entire Solar System, " he said. "It has a mass 6.5 billion times that of the Sun. And it is one of the heaviest black holes that we think exists. It is an absolute monster, the heavyweight champion of black holes in the Universe."

The image shows an intensely bright "ring of fire", as Prof Falcke describes it, surrounding a perfectly circular dark hole. The bright halo is caused by very heated gas falling into the hole. The light is brighter than all the billions of other stars in the galaxy combined-which is why it can be seen at such distance from Earth. The edge of the dark circle at the center is the point at which the gas enters the black hole, which is an object that has such a large gravitational pull (万有引力), not even light can escape.

"It is remarkable that the image we observe is so similar to that which we get from our calculations. So far, it looks like Einstein is correct once again. " Said Dr Ziri Younsi, of University College London-who is part of the EHT cooperation.

Chinese scientists were involved in the observation through a telescope in Hawaii. They were also highly involved in follow-up data processing and theoretical analysis, said Shen Zhiqiang, head of the Chinese Academy of Sciences' Shanghai Astronomical Observatory and a member of the EHT international team.

Shanghai and Taipei were selected as two of the cities to hold news conferences, together with Washington, Brussels, Santiago and Tokyo, a recognition of China's contribution.

"In the fields of astronomy, radio astronomy, and space astrophysics, China has made a significant contribution to this global project," Falcke said.

Many years ago, when we first went to Canada, we were driving through Montana with our two children. We thought we would find a motel(汽车旅馆) on the way and had not made a booking. As it was getting late, we started looking for a motel, only to find that all were booked, which worried me sick.

Finally, around 9 p.m., we stopped at a gas station to fill up the gas tank. My husband asked for a phone book and told the woman at the counter that we were trying to find a motel. He tried for 15 minutes. When he was unsuccessful, the woman, Linda, said she and her family lived nearby and would be happy if we spent the night at her home.

My husband was stunned by her offer. She called her son to direct us, since she had to hold the fort at the gas station till midnight.

When we reached her home, her husband greeted us. He took out two sleeping bags for the children. He invited us to have coffee and chat while we waited for his wife. When she came back, we asked if we could slip away in the morning so as not to disturb them. They said we were now guests and we would have to have breakfast with them.

We woke up to a table set for breakfast. They made a mountain of pancakes and bacon. We ate breakfast, and when we were leaving, my husband asked if he could offer some payment.

They insisted we were their guests. We left moved by their spirit of hospitality(好客). We were amazed that they would take in a family of total strangers from a different country. We kept in touch for many years. Over the years, we've lost touch with them, but have never forgotten their kindness.

A new study suggests lightning strikes that hit Earth after its formation may have un-locked a necessary chemical element to support the beginning of life. Researchers say the lightning may have supplied enough phosphorus（磷) to Earth during the first billion years after the planet was formed. Scientists believe life started on Earth about 3.5 to 4.5 billion years ago.

Phosphorus is an important element for the formation of life. It helps form cell structures and supports DNA, the material present in nearly all living organisms. But on early Earth, phosphorus is believed to have been first locked inside minerals that cannot dissolve in water.

Until now, it was widely believed that meteorites(陨石) that struck Earth were mainly responsible for the presence of "bioavailable" phosphorus. Some meteorites contain a phosphorus mineral called "Schreiber site" ,a highly reactive mineral that can form organic molecules.

But when lightning strikes the ground, it can create glassy rocks called "fulgurites" by superheating and sometimes vaporizing rocks on the surface. This process frees the phosphorus locked inside. As a result, these "fulgurites" can contain "Schreiber site", which can be dissolved in water, where life is thought to have formed.

The researchers say levels of phosphorus minerals caused by lightning strikes were found to have been higher about 3.5 billion years ago. The researchers think this was about the age of the earliest-known fossils widely accepted to be those of microorganisms. Scientists believe the earliest bacteria-like organisms were formed in Earth's early waters. But there is a debate over when this happened and whether it happened in warm and shallow waters or in deeper waters. New research does not completely cancel the theory that meteorites could have been an-other source of life-giving phosphorus. Meteor(流星)strikes around the time of the appearance of life are far less than thought a decade ago.

I earned about the zero waste movement in 2010 after reading a book about it in the library. It was eye-opening and encouraged me to remove as much single-use package as possible.

But as I followed the advice，I met many challenges. It turns out that small town Ontario isn't nearly as progressive as San Francisco when it comes to allowing reusable containers in grocery stores.

That's when I wished I still live in downtown Toronto which would give me access to many health food store that allowed reusable containers. It took a while, but finally I realized that my location give me one key advantage over city's people. I now live at the center of food production, which means I can go directly to producers to get ingredients that are not only package-free but the freshest and most delicious.

"Zero waste should be thought as more of an ideal than an hard-and-fast rule. It's so geographically independent on what is in your area, so I think it is about doing your best to make use of the resources you have. " said Celia Ristow, founder of a website. It is refreshing to see that fact accepted by others. It's true that the best-known zero waste supporters are city's people, who have access to many stores and restaurants that are willing to work with them.

However, wherever you are, it is impossible to find a places that meets all the ideals criteria. But that doesn't mean we should stop trying. The food scene in my small town has changed greatly in the past six years and far more reusable choices have been available than before. We have a food co-op that allows for online ordering and home delivering, many locations for dropping off milk bottles, a growing summer farmer's market and large pick-your own fruit farm.

I tell people and remind myself to remove what you can. Maybe the farmer's market share are only seasonal, and you have to be perfect, in fact, as the saying goes, "Perfection is the enemy of progress. "

Twenty-four trains, nine countries, 13,500 miles. They are the numbers behind the train journey one man took from Southampton in the UK to eastern China.

Roger Tyers, 37, spent a month on board trains and over $2,500 — almost three times of the cost of a return flight — to travel to the Chinese port city Ningbo for academic (学术的) research in May. It was the climate crisis, not a love of trains, that drove the sociologist to choose this hard route over a return flight. Tyers told CNN that he felt it necessary to stop flying when UN climate experts warned last year that the world has less than 11 years to avoid destructive levels of global warming.

Tyers is not the only person to avoid air travel in response to climate change. Thousands of people worldwide have publicly promised to stop flying, including teenage activist Greta Thunberg, who has encouraged youth climate protests around the world.

Activist Maja Rosen launched the "Flight Free" activity in Sweden in 2018 with the aim of encouraging 100, 000 people not to fly for one year. Although only around 14, 000 people signed the online "flightfree2019" promise, Rosen told CNN that the campaign had made more people realize the urgency of the climate crisis and motivated them to travel by train more often. Rosen, who stopped flying 12 years ago, says the collective promise helps deal with the sense of hopelessness many people feel when it comes to fighting with climate change. "One of the problems is that people feel there's no point in what you do singly. The activity is about making people realize that if we do this together, we can actually make a huge difference," she said.

Tyers calculated (计算)that his train journey to China produced almost 90% less emissions (气体排放)than a return flight.

Carl Wilhelm Scheele ranks as one of the greatest scientists of all time, but he paid a big price for this honor.

Born in 1742 in present-day Germany, Scheele learned about chemicals from his parents starting at a young age. When he was 14, he was sent away to Gothenburg (哥德堡) to become the apprentice (学徒) of a family friend. There he spent eight years studying chemistry and conducting experiments late into the night. Next, Scheele moved around the Holy Roman Empire, working for different chemists and becoming more learned in his trade. In 1767, he moved to Stockholm, where he discovered tartaric acid (酒石酸).

After three years in Stockholm, he became the director of the Locke Laboratory. It was there, while he was analyzing a strange reaction, that Scheele became the first person to identify oxygen.

He called the element "fire air" because he believed, based on the theories of his time, that a substance that made up fire was released from items when they burned. Scheele believed oxygen to be this substance, not understanding that oxygen is merely an element that facilitates (促进) the chemical reaction that is fire.

As historic as this discovery was, Scheele seldom got credit for it, largely because English scientist Joseph Priestley published findings on oxygen before Scheele, even though it is now generally accepted that Scheele made the actual discovery first.

Through his work, he thus exposed himself to many harmful materials. These chemicals had a deadly effect on Scheele, and he eventually died of kidney failure in 1786.

Sadly, in spite of his many achievements and the fact that he gave his life to chemistry, Carl Wilhelm Scheele is often forgotten in the history of science. Though he discovered many elements before other better-known scientists did, his unwillingness to both attend meetings of the Royal Swedish Academy of Sciences and to publish his work allowed other scientists to take credit for discoveries that he had made.

Have you kept the secrets in your heart? Have you tried to hide anything from others? Is it all right if you don't tell the truth? You'll find the answer after reading the following passage.

Marie was Joey's mother. There was something wrong with her son's feet. The doctor told her that Joey would be able to walk like others, but would never run very fast. At the age of eight, Joey ran around with the children in his neighborhood. His mother never told him that he wouldn't be able to run as fast as the other children. So he didn't know.

In the seventh grade, he decided to try out for a runner on his school team. He ran more than any of the others in order to be chosen. Joey practiced running four to five miles a day--even one day when he had a high fever. Although Marie was worried about him, she never told him he couldn't run with such a high fever. So he didn't know.

Two weeks later Joey made the team. Marie never told him he couldn't do it. So he didn't know. He just did it.

Although sometimes we don't tell others the truth, it can make them optimistic and meet the challenge of their lives bravely. Why not go for it?