I ______ sooner but I didn’t know that they were waiting for me.

A．had come

B．was coming

C．would come

D．would have come

对终板活动叙述错误的是（）

A.为非传播性的单向电位

B.呈负向偏转

C.低振幅

D.在扬声器中无声音

E.短时限