题干

滑块能沿静止的传送带匀速滑下,如图.若在下滑时突然开动传送带向上传动.此时滑块的运动将 (    )

A:维持原来匀速下滑

B:减速下滑

C:向上运动

D:可能相对地面不动.

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答案(点此获取答案解析)

A

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阅读下列短文,从文后各题所给的四个选项中选出一个最佳答案。

    An eight-year-oldgirl heard her parents talking about her little brother. All she knew was thathe was very sick and they had no money. Only a very expensive operation (手术)could  1 him now and there was no one to lend themthe money.

    When she heard her daddy say to her tearful mother, “Only a miracle (奇迹)can save him now,” the little girl went to her 2 and pulled all her money from itshiding place and counted it 3.

    She hurried to a drugstore(药店)withthe money 4 her hand. 

  “And what doyou want? asked the salesman. “It's for my little brother,” the girlanswered. “He's really, really 5 and I want to buy a miracle.”

  “Pardon?” said the salesman.

  “My brother Andrewhas  6  badgrowing inside his head and my daddy says only a miracle can save him. So howmuch does a miracle 7?”

  “8we don't sell a miracle here, child. I'm sorry,” the salesman said with a smile.

  “Listen, 9 it isn't enough, I can try and get some more. Just tell me 10 it costs.”

    A well-dressedman heard it and asked, “What kind of miracles does your brother need?”

  “I don't know,” she answered with her eyes full of  11. “He's really sick and mum says he needs an operation. But my daddy can't pay for it, so I have brought all my money.”

  “Howmuch do you have?” asked the man. “$ 1.11, butI can try and get some 12 money,” she answered.

  “Well, what a luck” smiled the man.“$ 1.11, the price of a miracle for little brothers.” He took up the girl's hand and said, “Take me to where you live. I want to see your  13 and meet your parents. Let's see if I havethe kind of miracle you need.”

    That well-dressed man was Dr. Carlton Armstrong, afamous 14. The operation was 15 and it wasn't long before Andrew was homeagain.