"The president's report," a smile on his face, he continued, "___ to several hot topics, discusses how to increase peasants' income．"

A．referring

B．refers

C．having referred

D．referred

心电图的QRS波代表（）

A.左右心房的去极化过程

B.左右心室的去极化过程

C.左右心室的复极化过程

D.左右心房的复极化过程

E.动作电位在心脏内的传导过程