Bài 1:
     1.a         2. d        3. a      4. c       5. c      6. b
Bài 2:
     1. cotaminated                                6. defeated
     2.                                                     7. abandoned
     3. located                                        8.  established
     4. exploring                                     9.
     5. orphan                                        10. contains
Bài 3:
     3. poisonous      8. tropical                10. independently
     4. conserving     9. contaminated
Bài 4: 
     1. had gone-would have become                          7. had had-would have sent
     2. had missed-would have been                           8. might have been-hadn't known
     3. could have gone-hadn't got                               9. had driven-wouldn't have happened
     4. would have been-had walked                           10. had told-could have lent
     5. would have forgot-hadn't reminded
     6. had had-would have taken
Bài 5:
     1. If he had prepared for the interview, he would have got the job.
     2. If we hadn't ran out of money, we wouldn't have come home from our holiday early.
     3. If I had enough free time, I could take much exercise.
     4. If the fire brigade hadn't come immediately, the house would have burned down.
     5. If the men hadn't been wearing protective clothing, they wouldn't have all quite safe.
     6. If people realised how important it is to conserve energy, they wouldn't do nothing about it.
     7. If I had known how dificult it was, I wouldn't have taken the job.
     8. If my father had earned much money, life would have been easy for us.
     9. If Daniel had had enough money, he would have bought the book.