____ You know. Mary is a bit slow ___ understanding so...

_____ So I have to be patient _____ him.

A．On; with

B．in; with

C．in;to

D．at;of

改善三相不平衡的措施正确的是（）。

A.使三相负载平衡分配

B.使不平衡负载分散连接

C.使不平衡负载集中连接

D.使不平衡负载接入更高的电网电压