单项选择题

针对χ、γ辐射，下列哪种材料的抗辐射性能最好？( )

A.6mm厚铅板
B.20mm厚铅玻璃
C.50mm厚铸铁
D.600mm厚黏土砖砌体

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单项选择题

某设计依据水文站，经用皮尔逊Ⅲ参数如下：洪峰流量Qmp均值为1000m3 s，Cv＝1.0，Cs＝2.5，ΦP（P＝5%）＝2.0，经推算二十年一遇洪峰流量的设计值Qmp为（）。

A.5000m3/s
B.4000m3/s
C.3000m3/s
D.2000m3/s

单项选择题

根据下面资料，回答21-35题Sometimes I feel that being the mother of three small children is like operating a large circus(马戏团)．21afternoon last week, my three sons playing peacefully in the back yard ( 院子),22the ball from one to another．I jumped at the chance to talk to one of my friends23the phone, but before I24to the phone, I could tell the boys had begun to quarrel with each other about something．I rushed out to25peace,but before I got there Charles had26a rock at Mark,and hit him in the eye．By the time I got to the back yard,they had begun to27about this．Even David,the oldest boy,who won' t usually fight with anybody about28,was involved(卷入) First,!29them stop fighting, and then ! examined Mark' s eye．I decided that it wasn' t going to develop into a black eye, but I felt that they should30at least a little for31they had done． I' m going to32to your father about this when he comes home tonight, I said． He and I will think of how to punish you． Things were33quiet after that for about half an hour, and then Charles34a glass in the kitchen,and at almost the same35,Mark fell out of the apple tree．第（24）题答案

A.went
B.came
C.reached
D.got

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