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问题 单项选择题

只有经过( )，公安机关的侦查活动才有合法的依据，才能行使侦查权力。

A．立案
B．上级允许
C．领导批准
D．法院证实

答案

参考答案：A

解析：立案是刑事诉讼的开端。

阅读理解

根据对话内容，从对话后的选项中选出能填入空白处的最佳选项，并将答案标号填写在答题卡上相应题号后的横线上。选项中有两项多余选项。

A：Frank，it’s almost vacation time．Have you found a summer job yet?

B： 小题1:  But camp job doesn’t pay much．How about you?

A：Well，I think I can get a j ob at the Friendship Hotel．A friend of mine was a waiter there last summer．The pay wasn’t good，but he got a lot of tips．He was happy with it．

B： 小题2: She enjoyed it．She said a restaurant was a good place for her．

A：小题3:After sitting in school classes all winter，I'd like a job in open air．

B：You are right．Everybody knows high school kids earn a lot just by cutting grass every summer．My brother is only fifteen，but he gets eight dollars every time he cuts somebody’s grass．It takes him only an hour!

A：小题4:But now，I think I might work for a building company，or something like that．

B：小题5:You can learn a 10t．

A：Well，I'd like to have a try．
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单项选择题 共用题干题

高速运行的电子将靶物质原子中某层轨道电子击脱，形成空穴。此时，外层（高能级）轨道电子向内层（低能级）空穴跃迁，释放能量，产生X线，称为特征辐射。特征X线的波长由跃迁电子能量差决定，与高速运行电子的能量无关。高速电子的能量可决定能够击脱某壳层的电子。管电压在70kVp以下时，电子产生的动能不能把钨靶原子的K壳层电子击脱，故不能产生K系特征X线。

与X线本质不同的是（）

A.无线电波

B.微波

C.超声波

D.红外线

E.γ射线
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