实验要求使用3μF的电容,需将1μF和2μF的电容( )。
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启辉器仅在荧光灯点亮时起作用,一旦荧光灯点亮后,启辉器就自动断路。此说法是( )。
A. ×
B. √
I didn't know the news until he told me.
The teacher will not on any account allow smoking in the classroom.
He had no sooner begun to speak than I sensed that something was wrong.
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