题干

入冬以来,全国多地多次发生雾霾天气,能见度不足20m.在这样的恶劣天气中,甲、乙两汽车在一条平直的单行道上,乙在前、甲在后同向行驶.某时刻两车司机同时听到前方有事故发生的警笛提示,同时开始刹车.两辆车刹车时的v﹣t图象如图,则(   )

A:若两车发生碰撞,开始刹车时两辆车的间距一定等于112.5m

B:若两车发生碰撞,开始刹车时两辆车的间距一定小于90m

C:若两车发生碰撞,则一定是在刹车后20s之内的某时刻发生相撞

D:若两车发生碰撞,则一定是在刹车后20s以后的某时刻发生相撞

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答案(点此获取答案解析)

C

同类题1

阅读下列短文,根据短文内容,从短文后各题所给的A、B、C、 D四个选项中,选择最佳选项。

How to Be a Better Student

    Maybe you are a common student. You probably think you will never be a top student. This is not necessary so, however. Anyone can become a better student if he or she wants to. Here's how:

Plan your time carefully. When you plan your week, you should make a list of things that you have to do. After making this list, you should make a schedule of your time. First set your time for eating, sleeping, dressing, etc. Then decide a good, regular time for studying. Don't forget to set aside enough time for entertainment. A weekly schedule may not solve all your problems, but it will force you to realize what is happening to your time.

    Find a good place to study. Look around the house for a good study area. Keep this space, which may be a desk or simply a corner of your room, free of everything but study materials. No games, radios, or television! When you sit down to study, concentrate on the subject.

    Make good use of your time in class. Take advantage of class time to listen to everything the teachers say. Really listening in class means less work later. Taking notes will help you remember what the teacher says.

    Study regularly. When you get home from school, go over your notes, review the important points that your teacher is going to discuss the next day, read that material. This will help you understand the next class. If you do these things regularly, the material will become more meaningful, and you will remember it longer.

    Develop a good attitude about tests. The purpose of a test is to show what you have learned about a subject. They help you remember your new knowledge. The world won't end if you don't pass a test, so don't be over worried.

    There are other methods that might help you with your studying. You will probably discover them after you have tried these.