肥厚型心肌病"SAM"征为（）。 A.二尖瓣前叶舒张期前向运动 B.

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问题单项选择题

肥厚型心肌病"SAM"征为（）。

A.二尖瓣前叶舒张期前向运动

B.二尖瓣前叶收缩期前向运动

C.二尖瓣前叶舒张期后向运动

D.二尖瓣前叶收缩期后向运动

E.以上均不是

答案

参考答案：B

单项选择题

吸引游客注意是预防游客走失的( )。

A．第一要务
B．关键措施
C．重要手段
D．无效方式

选择题

____several times，but unfortunately，the boy still couldn’t smooth away the problem on his own.

A．Having been explained

B．The problem having been explained

C．The problem had been explained

D．Although the problem had been explained