______________ twice a year, whether it is a car, a bus or a truck, is the rule that every driver must obey in this city.

A．Examining

B．Examined

C．Having been examined

D．Being examined

携带型短路接地线的操作棒的工频耐压试验的周期是（）。

A.1年

B.2年

C.4年

D.以上都不是