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. had walked
D. has walked
答案:D
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. had walked
D. has walked
答案:D