在MGB1420万能磨床晶闸管直流调速系统控制回路的辅助环节中，由R

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问题单项选择题

在MGB1420万能磨床晶闸管直流调速系统控制回路的辅助环节中，由R29、（）、R38组成电压负反馈电路。

A、R27

B、R26

C、R36

D、R37

答案

参考答案：C

填空题

根据下列句子的意思及所给的汉语提示, 写出空缺处单词、固定短语或固定搭配的正确形式。

1. This is the _______ (双胞胎) room. Yours is over there.

2. She _______ (表达) her thanks to us when we met.

3. Do you mind (准备) supper? I'm too busy to do it.

4. Don't _______ (生气的) with me! It's not my fault.

5. Speak as _______ (有礼貌地) as you can to the old people and try not to be rude.

选择题

人体个体发育开始于

A．卵细胞

B．受精卵

C．胎儿

D．婴儿