洋地黄中毒反应引起的心律失常最多见的是（）。

A.一度房室传导阻滞

B.房性期前收缩

C.阵发性室上性心动过速

D.室性期前收缩

E.心房颤动

Only when he left his hometown and went abroad_______ he loved his parents very much.

A．has he realized

B．did he realize

C．he realized

D．he had realized