1 As my father___(leave)the house, the postman___(arrive).
2.Tom___(work)in the garden while i ___(sit) in the sun.
3.As i ___(walk)down the street. i___(meet)Charlie.
4.While he ___(read)the letter, he __(hear)a knock at the door.
5.While mother___(prepare)lunch,Janet___(set)the table.
6.She___(drop)the tray when i___(speak)to her.
參考答案:1.had left ; arrived（都发生在过去，而离开更在之前）
2.worked ; sat(这句里的while表示的应该是一种对比)
3.was walking ; met（表示事情同时发生，下同）
4.was reading ; heard
5.was preparing ; set
6.dropped ; was speaking