（）．
参考答案：
Kathy didn't know _____ or not. [ ]
A. if her mother liked animals
B. her mother whether liked animals
C. whether did her mother like animals
D. whether her mother liked animals
在电力系统中常用的互感器为（）的。
A、加极性
B、减极性
C、正极性
D、负极性
（）．
（）．