下列哪项改变不是人工心脏起搏的指征()
A.病窦综合征
B.完全性房室传导阻滞
C.频发房性早搏
D.二度房室传导阻滞有阿-斯综合征
E.三度窦房传导阻滞
参考答案:C
The microscope opened up to man another strange new world: a world of things too near and small for anyone ______ the scientist to know much about or do much about.
A.besides
B.apart from
C.but
D.without
电器按执行功能可分为几类?