题干

在巴塞罗那奥运会上,运动员用带火的弓箭点燃奥运圣火,这个过程中(  )

A:箭能射出去是因为箭具有弹性势能

B:弓拉得越紧,运动时的弹性势能越大

C:弓拉得越紧,弓的弹性势能越大

D:弓拉得越紧,弓上的箭的弹性势能越大

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答案(点此获取答案解析)

C

同类题3

     My parents used to tell me how important school was for me, but I didn't think so. I paid little attention to it. But one thing let me finally 1 what my parents meant.
     One day, when I   2   a mobile phone store, I saw an advertisement on its door. It was hiring new workers!
“Sir, are you hiring people?” I went   3  the shop and asked. “Yes, but you should be the man who we need,” the manager answered. He looked at me for a few   4 from head to foot. “Do you have a high school diploma(文凭)?” 5 he, “Or do you have any work experience?”
    I felt so ashamed and  6 that I didn't know what to say, so I just turned around and left. I could not fall asleep that night, and I thought a lot about my  7  . “I must go to school or I can’t do anything without a good education,” I  8 to myself silently. I never went back to the store again 9 I finished my study and got a diploma.
10 looked the same when I returned to the store: the same people and the same design. However, compared with last time, I had more  11  . The manager told me they needed new    12  . So it was a great chance for me.
    I 13  my diploma to the manager. He looked at it and said, “Great, you are in.”
    Now I am still working in the same store. With this experience, I always  14 people to attend school. Education helps you have a bright future. Now I am not worried about my future because I'm still   15in my spare time.