IV/

1. We were quite tired because we worked very hard in the garden

2. Nam went to bed early because he was tired

3. Lan is very busy because she is having her final examination

4. Ba felt worried because he had a serious toothache

5. Mai had a nice gift because she studied hard this school year

6. We had to start very early this morning because we didn't want to miss the bus

7. Tam is sad because she misses her parents

8. The machine doesn't work because there is no electricity

9. Hoa brushes her teeth regularly because she doesn't want to have cavities in her teeth

10. We go to Nha Trang this summer because we want to visit Tri Nguyen Aquarium

V/

1. j

2. h

3. g

4. f

5. a

6. b

7. c

8. i

9. e

10. d

VI/

1. Why do you look tired?

Because I stayed up late last night

2. Why do you enjoy Physical Education?

Because it helps me keep fit

3. Why did you call doctor last night?

Because my mother was sick

4. Why did you take aspirins

Because I had an headache

5. Why did you leave the party early last night?

Because I had an appointment with my friends

6. Why does Nam have toothache?

Because he eats too much candy every day

7. Why did Mai visit Ha Noi last summer?

Because she want to visit her relatives and friends

8. Why are you pleased?

Because my tooth stops hurt

VII/

1. Where

2. matter

3. toothache

4. meeting

5. in

6. am

7. filled

8. hurt

VIII/

1. Brushing your teeth is very important

2. Hoa received a letter from her mother yesterday

3. The dentist told Minh not to forget to brush his teeth

4. How often do you brush your teeth?

5. How do most children feel when they come to see the dentist?

6. I ironed clothes for my father yesterday

7. How often do you go shopping?

8. I often wash and iron my own clothes. 

IV.

1. we were quite tired because we worked very hard in the garden
2. Nam went to bed early becuase he was tired
3. Lan is very busy because she is having her final examination
4. Ba felt worried because he had a serious toothache
5. Mai had a nice gift because she studied hard this chool year
6. we had to start very early this morning because we didn't want to miss the bus
7. Tam is sad because she misses her parents
8. the machine doesn't work because there is no electricity
9. Hoa brushes her teeth regularly because she doesn't want to have cavities in her teeth
10. we go to Nha Trang this summer because we want to visit Tri Nguyen Aquarium

V.

1- f 

2- h

3-g

4- j

5-a

6-b

7-c

8-i

9-e

10-d