控制性降压期间发生快速耐受性的原因有（）

A.交感神经张力增加

B.血浆儿茶酚胺增加

C.血管紧张素增加

D.内皮素增加

E.血管升压素增加

_____ many times, but he still didn’t know what to do next.

A．Having been told

B．Although he had been told

C．He had been told

D．Having told