任何一个完整的电路都必须由_、_、_三个基本部分组成,电路的作用是对电能进行_和_,对电信号进行_和_,电源或信号源产生的电压和电流称为_,相应在电路元件上产生的电压和电流称为_
You can _____ some bottles of wine, or some chocolates, or a bunch of flowers.
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
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