Some people believe that they would be better off     more adaptive activities in their leisure time, such as establishing relationships and teaching their children．

A．doing

B．to do

C．having done

D．to be doing

电力电缆安装前要进行检查，对lkV以下的电缆进线检查的内容是()。

A.直流耐压试验 

B.交流耐压实验 

C.用500V摇表测绝缘 

D.用1000V摇表测绝缘