Teenagers           their health because they play computer games too much.

A．have damaged

B．are damaging

C．damaged

D．will damage

支气管扩张症最常见的病因是（）

A.支气管内结石

B.肺结核

C.肿瘤压迫

D.肺囊性纤维化

E.严重的支气管肺部感染和支气管阻塞