Respuesta:
2. two boys were playing soccer when the teacher came into the classroom
3. i was running to the park when i heard a terrible noise
4. while tony was cleaning the bathroom, his son shouted in the kitchen
5. my son broke his pencil while he was doing his homework
6. i was waiting for my friend when the bus arrived
Explicación:
1. the students were doing an exercise when the bell rang
2. i saw an accident while i was waiting at the bus stop
3. when she was writing an email, her computer turned off
4. he fell down when he was climbing a tree
5. when my mom came home, my sister was sleeping
6. we found some old photographs when we were tidying our room
7. when you called me last night, i was studying for the test
8. i had a bad dream when i was sleeping in the sofa
9. when the fire alarm went off, we were listening to music
10. she started to cry while she was watching a movie
