题目

 --What _________ you do last night?  -- I ___________ my homework. A. do, do                  B. do, did                     C. did, does           D. did, did 答案：D9．以10m/s的速度行驶的汽车，紧急刹车后的加速度大小是2m/s2，则6s内的总位移为（　　）A．0B．16mC．24mD．25m