题干

“尾气催化转换器”将汽车尾气中的有毒气体转变为无毒气体.其微观过程如图所示,其中不同的圆球代表不同的原子.下列说法中正确的是(  )

A:生成物全部是化合物

B:参加反应的两种分子个数比为3:2

C:反应后分子个数变少了

D:反应后原子个数变少了

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答案(点此获取答案解析)

C

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阅读理解

    Buttons are found on all sorts of clothing. They are usually small and round and made of metal or plastic. They fasten, or connect, one piece of clothing to another. They make sure your clothes don't fall off. When we are speaking or writing m English, buttons can be just as useful.

    Men or women often wear button-down clothes to the office. Button-down as an adjective means to be conservative(保守的)or traditional. People who are described as buttoned-down stay close as possible to the normal way of dressing and behaving. They don't wear crazy clothing or do unusual things. People and events can both be described as buttoned-down.

    If someone is buttoned-up, he or she seems very business-like. In personal relationships, a buttoned-up person is cold and standoffish, meaning they physically and emotionally keep away from others. Buttoned-up people are not warm or friendly. And they do not share their inner thoughts and feelings with others.

    In the expression “button up”, button is a verb. It means to stop talking. Now, let's say you find yourself buttonholed in a conversation at a party. The person just keeps talking and talking and talking! Finally, you can't take it any longer. You tell the person to button it! This is a direct, but unacceptable way of saying “stop talking”. Button you lip is another equally rude but effective to stop a person who talks too much.

    Another kind of difficult person is someone who pushes your buttons. To push someone's buttons means to know exactly how to get that person angry or upset. People who like to push other people s buttons usually do it for selfish reasons. First they find a person's weak point. Then they use it to upset him.