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问题 不定项选择

如图所示，两光滑平行导轨水平放置在匀强磁场中，磁场垂直导轨所在平面，金属棒ab可沿导轨自由滑动，导轨一端跨接一个定值电阻R，导轨电阻不计。现将金属棒沿导轨由静止向右拉，若保持拉力F恒定，经时间t1后速度为v，加速度为a1，最终以速度2v做匀速运动；若保持拉力的功率P恒定，棒由静止经时间t2后速度为v，加速度为a2，最终也以速度2v做匀速运动，则

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A．t2＝t1　　　　　

B．t1>t2

C．a2＝2a1

D．a2＝3a1

答案

BD

填空题

阅读短文，从方框中选择适当的动词，并用其适当形式填空。有的需要加助动词或不定式符号。（每词限用一次）

have   knock    happen   call   work   

Last weekend, Jim went to see a film. It was about a boy 1___________Bob. Bob lived with his parents in a small town. They were very poor. Bob’s father 2___________ in a market for a long time. Bob wanted 3___________a bike very much.

One day, an old man 4___________down by some boys, and they ran away. Bob went to help the old man. The old man gave him a magic book and told Bob to make a wish before opening it.

Can you guess what 5___________ in the end? Please watch the film and find out!
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单项选择题 B型题

胃脘胀痛，痛连胁肋，嗳气痛减，证属（）

A．气滞

B．痰饮

C．血虚

D．肺热

E．真心痛
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