By the time he realizes he into a trap it'll be late for him to do anything about it．A.

问题补充：

By the time he realizes he into a trap, itll be late for him to do anything about it．

A. walks

B. walked

C. has walked

D. had walked

答案：

A. walks

B. walked

(答案→)C. has walked

D. had walked

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