胺碘酮的主要作用机制是（）
A.抑制钠内流
B.抑制钙内流
C.抑制钾内流
D.阻断β受体
E.延长动作电位时间
参考答案：E
I didn’t understand ________________ , so I raised my hand to ask him.
A．what my teacher says
B．what does my teacher say
C．what my teacher said
D．what did my teacher say
（）由国家税务总局规定。
A、增值税专用发票
B、发票防伪专用品的生产企业
C、全国统一发票监制章的式样印刷要求
D、全国统一发票的版面印刷要求
