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问题 单项选择题

在年平均雷电日大于30天的地区，配电变压器低压侧每相装设低压避雷器的目的是降低变压器受到（）过电压损坏的风险。

A.反击

B.正变换

C.反变换

D.直接

答案

参考答案：C

选择题

Last year, he wrote to tell me that he ______ his new dance. But I ______ of him ever since.

A．practised; didn’t heard

B．has practised; haven’t heard

C．was practising; hadn’t heard

D．was practising; haven’t heard
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单项选择题

The CPU does not have to look (66) all of RAM to find the spot it needs. But RAM only (67) the data temporarily. As soon as you switch the computer (68) , all that information disappears from the RAM. When you switch the computer on again, the RAM is (69) , and ready (70) a new program and new data.

（66）处填（）。

A．on

B．through

C．for

D．down upon
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