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问题 单项选择题

用10居里的铱192射源在野外对距其1米处厚20毫米的钢进行透照拍片，已知该射源的电离常数为0.6Rhm/Ci，对钢的半值层为10毫米，为了获得2.0黑度的底片需要曝光多少分钟？（）

A、10

B、20

C、30

D、40

答案

参考答案：B

单项选择题

Rapid application development (RAD) systems purport to lighten the developer’s (46) by making it easy to program an application with simple intuitive steps.
RAD tools (47) the developer everything needed to construct a fully functional application quickly and easily. They make short work of modifying the developed product to (48) changes after the program is finished. Applications developed with RAD tools are constructed as they are envisioned. As an application’s real usefulness (49) , the developer armed with RAD tools should be able to (50) on new features with little fuss.

A. offer B. order C. refer D. release
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问答题

单位正在进行正科长职位的竞聘活动，请你就此发表一篇竞聘演讲。
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