I

1b

2a

3a

4a

5a

6d

7b

8a

II

1d

2a

3c

4d

5a

6b

7b

8c

IV

1 came/had fished 

2 had met

3 went/ had read

4 hadn't worn

5 had started

6 does/did

7 lived/moved

8 told/learned

9 had worked/retired

10 got/had already started

11 came/had changed

12 had grown

13 came/had waited

14 has gone/ went

chúc bạn học tốt

I 

1.b

2.a

3.a

4.a

5.a

6.d

7.b

8.c

III.

1.the environment is affected in many ways by pollution

3.chemicals are being overused in their crops by some famers

IV.

1.came/ had finished

2.had met

3.went/ had read

4.hadn't worn

5.had started

6.had done/ went

7. has lived

8.told/ had learnt

9.had worked/ retired

10.got/ had already started

11.came/had changed

12.had grown

13.came / had waited

14.had gone/ went