---Whoareyougoingwith?---________.A.Myfather'sB.MyfatherisC.MyfatherD.M

---Who are you going with?---________.A.My father'sB.My father isC.My fatherD.My father is going

C解析完整的回答应该是I'm going with my father. with为介词，后面接宾语．

就是这个解释