In my opinion, life in the twentyfirst century is much easier than           .    [ ]

A. that used to be    

B. it is used to    

C. it was used to    

D. it used to be

当接触网作业车工作完毕，升降回转作业平台上、下所有开关必须置（）位。

A.最小

B.中间

C.最大