Bai 1:

3, I was preparing the lunch.

4, I was playing badminton with my friend.

5, I was doing morning exercises.

6, I was dancing with Tim.

Bai 2:

2, … was cooking dinner.

3, … were walking in Le Loi street.

4, … was studying for the coming exam.

5, … was watching.

Bai 3:

1, didn’t see; was looking

2, met; were going; was going; had; were waiting

3, was cycling; stepped; was going; managed; didn’t hit

Bai 4:

2, were you doing

3, Did you go

4, were you driving; happened

5, took; was not looking

6, didn’t know

7, saw; was trying

8, was walking; heard; was following; started

9, wanted

10, dropped; was doing; didn’t break