问题补充：
---I have finished my homework already, Mum.
--- When you it?
A. did; finished
B. did; finish
C. have; finished
D. were; finishing
答案：
A. did; finished
(答案→)B. did; finish
C. have; finished
D. were; finishing
解析：句意：妈妈，我已经完成了我的家庭作业。——你什么时候完成的？结合语境可知下文指的是过去某时发生的动作，故用一般过去时态，选B。
