Ⅱ型呼吸衰竭最主要的发生机制是（）
A.通气/血流>0.8
B.通气/血流<0.8
C.弥散功能障碍
D.肺动-静脉样分流
E.肺泡通气不足
参考答案：E
—Tom is never late for work. Why is he absent today?
—Something _____ to him.[ ]
A. must happen
B. should have happened
C. could have happened
D. must have happened
AUTOPILOT灯由（）控制
A、主FCC
B、从FCC
C、任一FCC
D、EICAS
