时态填空 -The classroom is so clean.When__you___it(clean)it?-We cleaned it twenty minutes ago.
问题描述：
时态填空 -The classroom is so clean.When__you___it(clean)it?-We cleaned it twenty minutes ago.
答
did clean可用have cleaned吗，强调过去打扫后对现在造成的影响但是后面有时间 暗示啊ago