问题补充：
Tom, you leave all your clothes on the floor like this!
A. wouldn’t
B. mustn’t
C. needn’t
D. may not
答案：
A. wouldn’t
B. mustn’t
(答案→)C. needn’t
D. may not
解析：本句是一个主从复合句，主句含有情态动词can，动作go还未发生，属于将来时；因此，when引导的时间状语从句要用现在时；当go动作发生时，finish动作已经完成了，故选 C。当然，空格出还可以用finish。如：
She will go to bed when she has done/ finishes her homework.
You can go to play football if you have finished your work.
