-- Is Mr Smith really very ill?   --________. He's in hospital.

A．I don't think so

B．No, he isn't

C．I hope so

D．I'm afraid so

阻塞性肺气肿的诊断，最有价值的是（）

A.PaO＜正常

B.潮气量低于正常

C.肺活量降低

D.残气量／肺总量＞40％

E.PaCO＞正常