母线的倒换操作，必须使用（）开关。
参考答案：母联
He left ________with my secretary that he would call again in the afternoon and he did keep his______. [ ]
A. words; words
B. word; words
C. word; word
D. the word; words
连词成句。
1. your, is, What, Hobby (?)
_________________________________________________________
2. stamps, like, collecting, I (.)
3. He, collecting, likes, too, stamps (.)
