The air cycle machine consists of a_____ (涡轮) and a ______ (压气机)

The air cycle machine consists of a_____ (涡轮) and a ______ (压气机)mounted on a common shaft.

A.turbine wheel,compressor wheel;

B.compressor wheel,turbine wheel;

C.left pack,right pack;

D.right pack,left pack;

正确答案是A