By the time he realizes he ____ into a trap, it’ll be too late for him to do any

题型：不详难度：来源：

By the time he realizes he ____ into a trap, it’ll be too late for him to do anything about it.

A．walks

B．walked

C．has walked

D．had walked

答案

C

解析

句意为：到他意识到已经进入一个圈套的时候，对于他来说做任何事情也都为时已晚了。与by the time 连用的句子应该用什么时态， 主要是看这个时间点发生在过去还是现在或将来。句中he realizes是现在的时间点，所以要用现在完成时，如By the time he is ten, he has outgrown his older brother. 他十岁的时候就已经长得比他哥哥高了。D项一般是从句为一般过去时的时候，主句才用过去完成时。