过去进行时：was/were doing — 英语词汇题

选择填空：Last Saturday was Ben's birthday. When his friends came in at 6:30 in the evening, Ben and his mother ___ the birthday cake in the kitchen, and his father ___ the balloons. A. was making; was blowing B. were making; was blowing C. were making; were blowing D. was making; were blowing