Only when we saw the photos about the air crash ________ how terrible it was. [ ]

A. had we known  

B. we had known

C. did we know  

D. we knew

患者，男性，52岁，体育老师。游泳课时突然出现胸痛，休息后无缓解。呼叫救护车，医护到场后检查，BP90／60mmHg，R12次／分，神清，双肺呼吸音清，HR80次／分，偶可闻及早搏，EKG提示：V1～V5ST段抬高，偶有室性期前收缩。回院途中，突然抽搐，意识丧失，唇面发绀，大动脉搏动消失。

患者最可能是（）。

A.Ⅲ度AVB

B.窒息

C.室颤

D.房颤

E.主动脉夹层破裂