计数器的主要功能是对（）进行计数，它主要由（）和（）组成。
参考答案：脉冲信号；触发器；门电路
She must be looking forward as much to his return as he himself is to________her. [ ]
A. see
B. have seen
C. seeing
D. be seeing
相序表是检测电源相位的电工仪表。（）
