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问题 不定项选择

在奥运比赛项目中，高台跳水是我国运动员的强项。质量为m的跳水运动员进入水中后受到水的阻力而做减速运动，设水对他的阻力大小恒为F，那么在他减速下降高度为h的过程中，下列说法正确的是（g为当地的重力加速度）[ ]

A．他的动能减少了Fh

B．他的重力势能增加了mgh

C．他的机械能减少了（F－mg）h

D．他的机械能减少了Fh

答案

答案：D

单项选择题

Ban the Band

Every year, our school has a dance for all the students. It’s a little funny seeing friends in clean shoes and trousers or colorful (1) , instead of the usual school uniform.

Most of us think the dance is great (2) even the teachers enjoy being there. (3) , two weeks ago someone said that there would be no (4) band this year— only CDs. "I don’t (5) it!" Amy cried out during the lunch break.

"Someone said the school couldn’t (6) a band, and they think it’s too noisy anyway, "added Daniel.

"Well, I don’t think it’s (7) enough without a band!" declared Angela, "and I’m going to see what can be done. "

Angela was as good as her (8) . In the afternoon she went to see the school headmaster who agreed to give the (9) some more thought. And he suggested that one (10) for having a band was to increase the price of each ticket from MYM5 to MYM10. Angela had to (11) out whether the students would like to do that."I need all of you to help me, " she (12) to our group before school the next day. "Mr. Berry gave me a list of all the names, and suggested we ask each one their (13) about the band and the extra cost. " (14) the day we asked around as Angela suggested, and wrote down people’s feelings about the band and the cost. We were amazed how much (15) there was for the band and everyone agreed to pay the extra MYMS."I’m surprised, " smiled Mr. Berry, when we gave him the (16) . "I really thought that only a few people (17) their band and that the cost would be too high. OK. Angela, your next (18) is to find a good band and line them up for the dance. "Angela was all smiles and (19) the news to Amy and Daniel. "You’re (20) , " smiled Daniel to Angela as he thought how close they came to having a less than perfect dance.

11（）

A.call 

B.find 

C.carry 

D.point
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单项选择题

标记环网使用 ______ 类型的网桥。

A．源路径透明桥

B．源路径选择桥

C．转换桥

D．生成树
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