变电所电气常用主接线形式有（）。
A、单母线；
B、双母线；
C、1/3接线；
D、桥形接线。
参考答案：A, B, D
中华人民共和国( )在法律面前一律平等。
A．人民
B．公民
C．选民
D．居民
Some people worry they are heavier than their friends, so they _____ breakfast. This is a bad idea. [ ]
A. don't eat
B. haven't eaten
C. hadn't eaten
D. didn't eat
