支气管炎(B型)慢性阻塞性肺气肿的临床特征是
A.多见于老年人B.气喘多呈持续性C.肺呼吸音明显降低D.PaO2显著降低E.PaCO2一般正常
参考答案:D
我国疆域辽阔,陆地领土面积约为______平方千米,与整个______洲的面积差不多.
I have a laptop _____ I don't often use it. [ ]
A. and
B. so
C. or
D. but