问题补充:
-- your homework yet?
-- Not yet. I it.
A. Have you done; am doing
B. Did you do; am doing
C. Have you done; did
D. Did you do; did
答案:
A. Have you done; am doing
B. Did you do; am doing
C. Have you done; did
D. Did you do; did
解析:考查动词时态。句意 你做完作业了吗?没有,我正在做。haven done 强调还没有做这个概念, 而 am doing 是说马上要做,口语中常说的(这时现在进行时表将来的概念,例如Im coming. Im going to school),所以选A项。