急性主动脉瓣关闭不全的病因包括（）
A.感染性心内膜炎
B.先天性畸形
C.主动脉夹层
D.人工瓣撕裂
E.创伤
参考答案：A, C, D, E
-- How are you getting on with your deskmate?
-- She is the last one I want to talk to . __________ .
A She has turned me in B She is always turning me off
C She had said bad words behind me D She turns me out
岩石中的天然放射性元素主要是（）、（）、（）三种。
