二尖瓣开瓣音可出现于()
A.二尖瓣关闭不全
B.左心房黏液瘤
C.二尖瓣狭窄
D.缩窄性心包炎
E.二尖瓣脱垂
参考答案:C
My brother left school in 2005,and since then he ________ in Beijing.[ ]
A. lives
B. lived
C. will live
D. has lived
矿石船装货结束前,应()。
A.观测船舶吃水
B.调整船舶浮态
C.确认各压载舱排水状况
D.以上都是