—________ you called yesterday evening?

—My sister. Why?[ ]

A. Who it is that  

B. Who is it that

C. Who was it that  

D. Who it was that

当血钾浓度增加至正常的3倍时心脏会有什么变化（）。

A.心率加快

B.心跳停止在舒张期

C.心跳停止在收缩期

D.心率减慢

E.不发生变化