题目

He helped his mother clean the rooms and then ____ his homework yesterday afternoon.    A. do      B.doing       C. does       D. did 答案：D东东爸爸出差回来对东东说：“我坐火车回来，当行驶到全程的13时开始睡觉，醒来时问列车员：离终点站还有多少路程？列车员说：还有你睡觉时所行驶路程的13．你知道我睡觉时火车所行驶的路程占全程的几分之几？你能解决这个问题吗？