It is reported that China is developing ________ emergency plan to solve ________ traffic jam crisis in

Beijing. [ ]

A. the; the

B. an; /

C. an; the

D. /; the

机场的假定零点高度是以（）气压面为基准。

A、机场基准面气压

B、修正海平面气压

C、标准海平面气压

D、实际地面气压