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有了化学方程式，我们就能够根据质量作用定律写出它的速率方程。

【参考答案】

(7)错误只有对元反应，才能根据质量作用定律直接写出它的速率方程。复合反应的速率方程由实验确定，不能直接根据质量作用定律......

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听力原文： A Brown University sleep researcher has some advice for people who run high schools: Dont start classes so early in the morning. It may not be that the students who nod off at their desks are lazy. And it may not be that their parents have failed to enforce bedtimE.Instead, it may be biologically that these sleepyhead students arent used to the early hour. 'Maybe these kids are being asked to rise at the wrong time for their bodies,' says Mary Carskadon, a professor looking at problems of adolescent sleep at Browns School of MedicinE.Carskadon is trying to understand more about the effects of early school time on adolescents. And at a more basic level, she and her team are trying to learn more about how the biological changes of adolescence affect sleep needs and patterns. Carskadon says her work suggests that adolescents may need more sleep than they did at childhood, not less, as commonly thought. Sleep patterns change during adolescence, as any parent of an adolescent can provE.Most adolescents prefer to stay up later at night and sleep later in the morning. But its not just a matter of choice — their bodies are going through a change of sleep patterns. All of this makes the transfer from middle school to high school — which may start one hour earlier in the morning — all the more difficult, Carskadon says. With their increased need for sleep and their biological clocks set on the 'sleep late, rise late' pattern, adolescents are up against difficulties when it comes to trying to be up by 5 or 6 am for a 7:30 am first bell. A short sleep on a desktop may be their bodys way of saying, 'I need a timeout.' Questions 16 to 18 are based on the passage you have just hearD.16. Why does Carskadon suggest that high schools should not start classes so early in the morning? 17. What might be a reason for the hard transfer from middle school to high school? 18. What is the passage mainly about?17．A.Adolescents sleep better than they did at childhooD.B.Adolescents have to choose their sleep patterns.C.Adolescents need more sleep than they used to.D.Adolescents depend more on their parents.

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听力原文：M: Hello, Mary. Fancy meeting you here! W: Hi, Peter. Yes, Im here again, there always seems to be a queuE.Im writing a report for my economics class. How about you? M: Im still working on my essay on environmental sciencE.I need to check out a referencE.W: You know, when I first started doing my report I was frightened to use these computer catalogues. I feared something would go wrong. M: But theyre so useful. You can see at a glance what books you need and if theyre checked out or not. W: I know that now, but at the beginning I really missed the card catalogues. But anyway I still have the same problem I used to have, knowing what to look up! M: Yes, I agree, its the same for mE.Last week I must have wasted two hours looking for information on a topic I was working on. W: Really? What was the topic? M: It was about the effect of smoking by parents on their childrens sleep. I looked up sleeping, child psychology, child development, problems in social work, childrens medical problems, and I cant remember what elsE.In the end, I had to go back and ask my tutor for help. W: You know, I took a study skills class because I thought it would help me locate information, and all I learned was how to read the cards, which wasnt of much help! My real problem is knowing what card to look up. M: Yes, and that takes thinking! Pity the computer cant do that for us. W: Maybe it will some day. Oh, look, theres a free computer now. M: Yes, thanks. See you! Questions 13 to 15 are based on the conversation you have just hearD.13. What is the mans purpose to come here? 14. What can we learn from the conversation? 15. What is the man going to do soon?14．A.The computer doesn't work properly.B.Peter is writing an essay on environment.C.Mary is much better than Peter in using computers.D.Peter is taking a computer class which is helpful.

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