_____, the population of China is the largest in the world.

A．It is known that

B．As is well known

C．Which is well known

D．We all know that

普萘洛尔治疗最适宜于治疗的心律失常为（）

A.室上性心动过速

B.室性心动过缓

C.室性心动过速

D.心房纤颤

E.心室纤颤