当电力系统发生过负荷，系统（）和（）短路时，都不会产生零序分量。
参考答案：振荡；相间
My mother likes _____ TV, but she doesn't like _____ it now. [ ]
A. to watch; watching
B. watching; to watch
C. to watch; to watch
教学目标是教学活动的出发点，也是课堂教学的灵魂。（ ）
