问题
不定项选择
运动员用双手握住竖直的竹竿匀速上攀和匀速下滑，他所受的摩擦力分别是F1和F2，那么 [ ]
A．F1向下，F2向上，且F1=F2
B．F1向下，F2向上，且F1>F2
C．F1向上，F2向上，且F1=F2
D．F1向上，F2向下，且F1=F2
答案
答案：C
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运动员用双手握住竖直的竹竿匀速上攀和匀速下滑，他所受的摩擦力分别是F1和F2，那么 [ ]
A．F1向下，F2向上，且F1=F2
B．F1向下，F2向上，且F1>F2
C．F1向上，F2向上，且F1=F2
D．F1向上，F2向下，且F1=F2
答案：C
| 补全对话，用下面方框中所给的选项填入对话适合的地方。 | |
| A: 1______? B: David Green. A: 2______? B: I want to join the English club and improve my English. A: Ok. Please say something about yourself in English. B: Of course. My name is David Green. I'm 12… A: You speak English very well. 3______? B: No, I've never been to a foreign country. A: 4______? B: I've been studying English for five years. A: 5______? B: Because I want to travel all over the world, and I want to know more about English.
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