Cuu tôi va ạ

1When I was walking in the park, I saw a rainbow.
A past action that was happening: I was walking in the park
Another action interrupted: I saw a rainbow
 

2.When she was studying for her exam, she heard a loud noise.
A past action that was happening: she was studying for her exam
Another action interrupted: she heard a loud noise
 

3.When they were cooking dinner, the power went out.
A past action that was happening: they were cooking dinner
Another action interrupted: the power went out
 

4.When he was driving home, a deer ran across the road.
A past action that was happening: he was driving home
Another action interrupted: a deer ran across the road