Was it two years ago _____ they first met? [ ]
A. since
B. which
C. while
D. that
答案:D
供电系统中发生短路的类型通常有三相短路、两相短路和单相短路,对系统造成危害最严重的是( )。
A.单相短路
B.二相短路
C.三相短路
D.单相接地
选方宜
A.大定风珠
B.左归丸
C.醒脾汤
D.天麻钩藤饮
E.半夏白术天麻汤