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问题 单项选择题

晶闸管交流调压电路输出的电压与电流波形都是非正弦波，导通角（），即输出电压越低时，波形与正弦波差别越大。

A、越大

B、越小

C、等于90°

D、等于l80°

答案

参考答案：B

填空题

看图完成答句，一空一词。

1. Where are the boys?

    They are ______ the ______.

2.What are one group of the boys doing?

    They are______.

3.What are the other group of boys doing?

    They are ______.

4.Where are the three students standing?

    They are standing ______ a big ______.

5.What are they doing?

   They're ______ the basketball ______.
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单项选择题 A1/A2型题

下列哪项不属于内分泌腺的腺体？（）

A.甲状腺

B.肾上腺

C.腮腺

D.脑垂体

E.胰岛
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