by the time he realizes he ( )into a trap,it‘ll be too late

问题描述:

by the time he realizes he ( )into a trap,it‘ll be too late
A.walks B.walked
C.has walked D.had walked

D句意:当他意识到自己陷入圈套中时,已经太晚了.
“陷入圈套”的动作发生在他“意识到”之前,所以发生在过去的过去,用过去完成时表示.
今天是除夕,祝新年快乐喔