4. How fast/ you/ drive/ when/ accident/ happen?
----> How fast were you driving when the accident happened?
5. While/ Henry/ walk/ in the mountain/ he/ see/ a bear.
----> While Henry was walking in the mountain , he saw a bear
6. The students/ play/ a-game/ when/ the progressor/ arrive.( theo Hằng câu này là professor chứ )
---> The students were playing a game when the professor arrive 
7. Felix/ phone/ the five brigade/ when/ the cooker/ catch/ fire
-->Felix phoned the fire brigade when the cooked caught on fire.
8. Andy/ come/ out of/ the restaurant/ when/ he/ see/ Jenny
---> Andy was coming out of the restaurant when he saw Jenny
9. Anna/ spend/ a lot of money/ yesterday// she/ buy/ a dress/ which/ cost/ $100.
---> Anna spent a lot of money yesterday, she bought a dress which cost $100.
10. When Margaret/ open/ the door/ the phone/ ring
---> When Margaret was opening the door, the phone rang