支气管扩张最常见的原因是（）
A.肺结核
B.肿瘤压迫
C.肺囊性纤维化
D.严重的支气管-肺感染和支气管阻塞
E.支气管内结石
参考答案：D
Mr. Black decided to give up his farm and devoted all his time to_______those children living on the street.
A．help
B．being helped
C．be helping
D．helping
我国在股票发行工作中采用过哪几种发行方式
