—Where did you put your bag?—Oh,I --- I put it on the chair

—Where did you put your bag?—Oh,I ___ I put it on the chair because the phone rang as I ___ in.—Where did you put your bag?—Oh,I ___ I put it on the chair because the phone rang as I ___ in.A.remenbered;come B.A.remenbered;was comingA.remenber;come B.A.remenber;was coming答案选的是D,但我想知道C为什么不行.最后一个空为什么要填was coming?