心肌自律性最高的部位是（）。
A.窦房结
B.心房肌
C.心室肌
D.房室交界
E.浦肯野纤维
参考答案：A
____ I went to the seaside, I picked up a great many shells.
A．The first time
B．For the first time
C．At first
D．By the first time
直接引起心脏压力负荷过重的瓣膜病为
A．主动脉瓣狭窄
B．主动脉瓣关闭不全
C．二尖瓣狭窄
D．二尖瓣关闭不全
E．三尖瓣关闭不全
