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问题 单项选择题

测量低雷诺数，粘度大的流体的节流元件最好选用（）。

A、1/4圆喷嘴

B、标准喷嘴

C、标准孔板

D、文丘利管

答案

参考答案：A

单项选择题

在35kV设备上安全距离为1.5m的作业应填用（）。

A.第一种工作票

B.第二种工作票

C.带电作业工作票

D.紧急抢修单
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单项选择题

The achievements of the greatest minds in science could never have been reached if it had not been for the patient and accurate work of hundreds of other people.

A．has it not been

B．if it had been

C．if hasn't been

D．had it not been
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