端电压与电流有效值的乘积称视在功率，它表示已经做功的功率。（）
参考答案：错
---_______ one and a half months enough for the project to be finished?
---I am afraid not. The professor is ill and only after he recovers ________ go on with it.
A．Is; he can
B．Are; he can
C．Is; can he
D．Are; can he
由基尔霍夫第二定律可知，当电阻的电流方向与回路和绕行方向相同，则电阻上的电压降取（）。
A.正
B.负
C.零
D.不能确定
