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

A．Examining

B．Examined

C．Being examined

D．Having been examined

相对标高是以建筑的（）高度为零点参照点。

A、基础顶面

B、基础底面

C、室外地面

D、室内首层地面