重复接地的安全作用不包括（）。

A、改善架空线路的防雷性能

B、降低漏电设备的对地电压

C、减轻零线断开的危险

D、减轻线路过负荷的危险

— I wonder _______ he persuaded his father to give up smoking.

— He showed him pictures of lungs damaged by cigarettes. [ ]

A. it was how          

B. how was it that       

C. how it was          

D. how it was that