题目

I ____a story over the radio when my friend came to see me yesterday afternoon.A. heard                                       B. was hearingC. listened to                                D. was listening to      答案：D甲、乙两物体都作匀速直线运动．已知V甲：V乙=4：5，S甲：S乙=2：3，则甲、乙所用时间之比为t甲：t乙=    ．