题目

甲乙两人从同一起点出发，朝相同的终点做直线运动。甲在前一半路程的平均速度为2m／s，后一半路程的平均速度为3m／s；乙在前一半时间的平均速度是2m／s，后一半时问的平均速度为3m／s。则甲乙谁先到达终点（ ）A.甲B.乙C.同时到达D.无法确定 答案：【答案】B【解析】对于甲来说，设总路程为s ， 根据v甲===2.4m/s；对于乙来说，设总时间为t ， v乙===2.5m/s，因为v甲＜v乙 ， 所以乙先达到终点。所以答案是：B。  There is one language that is used in every country in the world. The people who use it are young and old,short and tall,thin and fat. It is everybody's second language. It is easy to un?derstand ,although you can't hear it. It is sign language.  When you wave to a friend who is across the street, you are using sign language. When you smile at someone, you are saying, "I want to be friendly"，but you are not using speech, you are using sign language. When you raise your hand in class, you are saying, " Please ask me. I think I know the correct answer.”Babies who can't talk can point at things. They are using sign language. A policeman who wants to stop traffic holds up his hands. He is using sign language.  Many years ago，a French priest，Charles Michel de Epee，became interested in education for deaf people. He invented a finger alphabet(字母表) .It is still in use. People can make the sign for letters and spell words with their hands，and deaf people can read and understand them. Soon there were schools for the deaf in many countries. The only university for the deaf is Gal-laudet College in Washington, D C.   Today, in the United States, there are special TV news programs for deaf people. The newsreader tells the news in sign language. At the same time,the words appear on the TV screen.   The actors in the Theatre of Deaf don't spell every word. Sometimes they use hand signs. When they put two hands together, it means sandwich. They can make a roof with their hands when they want to show a house. One finger in front of an actor's mouth can mean quiet. You can talk to people who are behind windows that are closed. And when you go swimming with your friends，you can have conversations under water.How many hand signs do you use every day? (   ) 1. The passage is mainly about        .   A.a famous priest inFrance   B.the importance of sign language   C.an introduction to sign language   D.how to use sign language(   ) 2. If you want to express the idea that "I am very friendly" to someone, you willA. raise your hand   B. put one hand onto the other   C. make a roof with your hands   D. smile to the person(   ) 3. Which of the following about sign language is true?   A.It is a special language used in a few countries in the world.   B.It is a way to express one's ideas without words.   C.It is only used by the deaf.   D. It can be heard.(   ) 4. According to the passage, which of the following is NOT a sign language?   A.You wave to your friend happily.   B.You raise your hand in the class.   C.A deaf people reads a passage aloud.   D.A policeman stops your car by holding up his hand.