Answers

Exercise 1

1) was waiting

2) wasn't working

3) was waiting

4) had

5) was driving

6) were you doing

7) didn't call

8) was still sleeping

9) Was it raining

10) was stopped

Exercise 2

1) were you doing, called

2) was sitting, called

3) arrived, was

4) was watching, heard

5) went, had, met

6) were playing, hurt

7) were they doing

8) reached, was

9) was, rang

10) walked, was working

11) was, was shining, were singing, was walking, met

12) was living, started

13) got, were waiting

14) was, was always leaving

15) visited, saw, spent

16) were you standing, came

17) lived, were

18) were listening

19) left, was snowing

20) was working, meet

Exercise 3
1) While I was driving, I had an accident.
2) Kate had dinner and then she did her homework.
3) The thieves were hiding in the kitchen when the police came in.
4) Sam planned a party and then he phoned his friends.
5) While we were cleaning the house, we broke some glasses.
6) Alan was looking out of the window when he saw a UFO.

Exercise 4
1) were playing
2) noticed
3) was having
4) saw 
5) fell
6) was hiding
7) broke
8) came 
9) was living
10) distracted

Test
1. spoken
2. caught
3. eaten
4. understood
5. begun

1. had given / 'd given
2. had seen / 'd seen
3. had heard / 'd heard
4. had cooked / 'd cooked
5. had lost / 'd lost

1. had not ordered / hadn't ordered
2. had not visited / hadn't visited
3. had not worn / hadn't worn
4. had not swum / hadn't swum
5. had not done / hadn't done

1. Had you finished
2.  had not you cleaned / hadn't you cleaned
3. Had you had
4. Had she managed
5. had she stayed

1. destroyed
2. cleaned
3. had already done / 'd already done
4. ate
5. had put on / 'd put on

1. had been trying
2. had already picked / 'd already picked
3. had been waiting
4. had already apologized / 'd already apologized
5. had been watching / 'd been watching