___ for the fact that you were lazy, you could have finished the assignment by now.

A．It were not

B．Weren’t it

C．Had it not been

D．Had not been

维拉帕米的抗心律失常作用包括

A．减低窦房结起搏细胞的自律性

B．减少或取消后除极引起的触发活动

C．减慢房室结的传导速度

D．延长房室结的有效不应期

E．与β受体阻断药或奎尼丁合用，可减少心脏毒性