历史上曾经在北京地区活动过的少数民族有（）
A.山戎
B.瓯越
C.乌桓
D.鲜卑
E.奚
参考答案：A, C, D, E
社区获得性肺炎患者对抗菌治疗无反应，应考虑下列哪些因素（）
A.患者有肺气肿
B.肺部二重感染
C.有隔离感染灶（如脓胸）的存在
D.致病菌耐药
E.抗菌药物剂量不足
31. The cheering went on for quite some time _____ it died down and people took their seats again.
A．Before
B．Since
C．As
D．When
