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问题
多项选择题
低压电动机应具备（）保护装置。
A.短路
B.过负荷
C.单相断线
D.远距离控制
答案
参考答案：A, B, C, D
填空题
命题：“直角三角形中，两直角边的平方和等于斜边的平方”的逆命题是______．
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选择题
Only when he read the newspaper _____ the US President Obama would deliver a speech in his university.
A. he knew
B. he had known
C. had he known
D. did he know
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