David ________ from the analysis of the traffic accident that it had been caused by human error.[ ]

A．announced  

B．acknowledged

C．concluded  

D．considered

下述哪项是蛛网膜下腔出血的病因（）

A.动静脉畸形

B.长段动脉膨胀（dolichoectatiC.

C.颅内肿瘤

D.Moyamoya病

E.真菌性动脉瘤