They must have done their homework yesterday,___? 为什么是didn't they? 我觉得应该是haven't they啊?
人气:392 ℃ 时间:2019-10-20 00:09:23
解答
must have done :对过去事实的推测,不是现在完成(后者不能与明确的过去时间连用).反义问句是问“昨天他们是否做了家庭作业”,当然用didn't they. 比较: They have done their homework,haven't they? They did their homework yesteday,didn't they?