1. When Don/ arrive/ have/ coffee 2. he/ sit down/ on a chair/ while/ I/ paint/ it 3. the students/ play a game/ when/ professor/ arrive 4. While/ he/ walk/ in the mountains/ Henry/ see/ a bear 5. I/ walk/ home/ when it/ start/ to rain 6. When/ Margaret/ open/ the door/ the phone/ ring

Đáp án : 

1. When Don arrived, we were  having coffee 

2. He sat down on a chair while I was painting it 

3. The students were playing game when professor arrived 

4. While Henry was walking in the mountains , he  saw a bear 

5. I was walking home when it started to rain 

6. When Margaret was openning the door , the phone rang