have finished
答完就交卷!为甚不用将来完成时一是理解成条件句：(You) hand in you papers when you havefinishedthe test .就是说： if you havefinishedthe test ,then hand in....另一种想法。(You) hand in you papers when you havefinishedthe test .主从句其实动作很近， 要保持一致的时态。