第一心音减弱不常见于
A．二尖瓣关闭不全
B．主动脉瓣关闭不全
C．二尖瓣狭窄
D．心肌炎
E．心肌梗死
参考答案：C
试述肺通气障碍的类型和原因。
He did not go into detail on the subject. He spoke _____. [ ]
A. in common
B. in particular
C. in general
D. in short
