用动词的适当形式填空。
1. While we __________ (wait) for the bus, a girl __________ (run) up to us.
2. I __________ (telephone) a friend when Bob __________ (come) in.
3. Jim __________ (jump) on the bus as it __________ (move) away.
4. We __________ (test) the new machine when the electricity __________ (go) off.
5. She __________ (not want) to stay in bed while the others ________________ (all, work) in the fields.
6. While mother ________ (put) Cathy to bed, the door bell ________ (ring).