题目

已知A、B两种元素形成的化合物中，A、B元素的质量比为2:3，其相对原子质量之     比为2:1，则该化合物的化学式为（     ）  A．A2B3                 B．A3B2            C．AB3              D．A3B 答案：CBedazzling (眼花缭乱) with their bright colors and eye-catching displays, fireworks light up our night skies during the holidays. However, these crowd-pleasers can have some damaging side effects. Once a firework is set off, it only takes a couple of seconds before smoke, dust and harmful chemicals are let out into the atmosphere. The loud booming noises are caused by gunpowder. While the sounds may excite some people, they can be frightening to domestic and wild animals—as well as some humans. The pretty colors you see are a result of more chemicals. Barium, added to make green, is known for its poisonous and radioactive qualities. Blue comes from copper compounds. Cadmium, lithium and lead—all found in fireworks—have been linked to diseases, such as allergies and skin rashes in both humans and animals. Acid rain has been linked to gases given off by fireworks, which sometimes go beyond the toxin(毒素) limits of the United States Clean Air Act. Once all those chemicals come back down to the ground, they can cause problems too. Debris (碎片) from the fireworks falls to the ground, where animals can burn their paws or noses on piping hot pieces. Humans also are at risk of stepping on or picking up something sharp or hot. Meanwhile, debris that finds its way into waterways can damage animal habitats and water supply sources.                               Instead of setting off fireworks, try to come up with some new ways for fun. Here are some ideas to get you started: • Sky lanterns—a tradition that originated long ago in the most-populated Asian country. •Party crackers—a favorite in the United Kingdom—give you noise and surprises without the mess of fireworks. You can make your own or buy eco-friendly crackers. •Want noise excitement with less volume? Consider a fireworks sound recording beforehand or break out the party horns (号角) and blow up a storm!  1．The advantages of fireworks can be seen below EXCEPT that _____.      A．the special sounds of fireworks excite people      B．debris from fireworks can even find its way into water      C．the pretty and bright colors add to the beauty of night skies      D．fireworks are enjoyed as one of the crowd-pleasers 2．Which of the following is NOT true according to the passage?   A．Copper compounds are needed to make green in fireworks.      B．Chemicals in fireworks are both poisonous and dangerous.      C．Too much gas from fireworks can result in acid rain.      D．Chemicals in fireworks are harmful in the air and on the ground. 3．All the italicized (斜体的) words are probably ____.      A．mineral materials                                  B．tiny solids      C．chemical elements                                D．broken pieces 4．What is implied from the passage?      A．Gunpowder in fireworks makes loud booming noises.      B．It must be Indians who first started to hang sky lanterns.      C．Fireworks do less harm in the air than on the ground.      D．Fireworks can even break the balance of nature. 5．What can be concluded as the writer’s attitude towards fireworks?    A．It is not allowed to set off fireworks except during the holidays.    B．Fireworks should be banned and replaced by some other means.    C．Night is the best time to set off fireworks and see the pretty colors.    D．You cannot set off fireworks unless you come up with new ways.