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问题 选择题
求如图所示的交变电流的有效值，其中每个周期的后半周期的图象为半个周期的正弦曲线（   ）

A．5A

B．5A

C．5/2A

D．/2A

答案

答案：C

填空题
当x=______时，
1
4
：x的比值恰巧是最小的合数．

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单项选择题

Questions 14-23


Look at the ten statements for this part.
·You will hear a passage about "Great Transformation. ". You will listen to it twice.
·Decide whether you think each statement is right(R), wrong(W) or not mentioned(NM).
·Mark your answers on the Answer Sheet

The Great Transformation is probably caused by the development of practical science.

A．Right

B．Wrong

C．Not Mentioned
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