可造成牙髓坏死的原因有()
A.深龋
B.畸形,中央尖折断
C.氟牙症
D.外伤
E.烟斑染色
参考答案:A, B, D
(2013·高考山东卷)Mark needs to learn Chinese ________ his company is opening a branch in Beijing.
A.unless
B.until
C.although
D.since
严重的三尖瓣关闭不全的晚期多出现()
A.左心室衰竭
B.房颤
C.室颤
D.全心衰竭
E.右心室衰竭