The secretary worked late into the night, _____ a long speech for the president.

A．to prepare

B．preparing

C．prepared

D．was preparing

TIA时常见的辅助检查表现为（）

A.头CT可见片状低密度影

B.脑电图大多正常

C.头MRI大多正常

D.TCD可见血管狭窄

E.以上全部