Respuesta:
1. Mrs. Brown was really surprised when she learnt/learned the news this morning.
2. While Mrs. Black was milking her cow, it was eating some grass.
3. Martin dropped the plate, while he was serving it.
4. While I was walking in the park yesterday, I saw an UFO.
5. When the telephone rang, George was having a shower.
6. Mrs. Smith saw Tom while he was talking on the phone.
7. While he was waiting for his girlfriend, he got very angry
8. David's pants fell down while he was walking in the street yesterday.
9. When her grandson knocked at the door, Mrs. Plump was knitting.
10. Martin first saw Jennifer while she was dancing at a party.
11. Bruce slipped on a soap and fell while he was cleaning the bathroom.
12. Joe was playing bowling with his friends when he dropped the ball on his foot.
13. When the brothers met after a long separation, they hugged each other tightly.
14. Adam’s papers fell from his briefcase while he was going to work.
15. While we were having a barbecue, Mike's pants caught fire.
16. When we looked out of the windw, it was raining heavily.
17. When my tooth fell out, I was eating cookies.
18. While I was swimming in the sea, I saw a shark just in front of me.