6. If he had studied his lessons very carefully, he wouldn’t get bad marks now
7. If I had had enough money, I would have bought that shirt
8. If he had asked us to help, we would have done
9. If Tom were taller, he could reach the shelf
10. If Joe weren’t a nephew of the director’s, he wouldn’t be promoted
11. If it hadn’t been for you help, he wouldn’t have been able to get the job
12. Had he had breakfast this morning, he wouldn’t feel so hungry now
13. Unless you tell me the reason, I won’t leave
14. Unless I were tired, I would join you there
15. Were I you, I would study harder
—
1. Unless other sources are found, our sources of energy will soon end
2. Unless nuclear tests stop, life on earth will be destroyed 
3. Unless other types of protein are found, men will continue to rise
4. Unless we try to reduce it, world population will continue to rise
5. Unless we do something to preserve all our beautiful forests, they will be destroyed
—
1. Reads
2. Were - would visit
3. Have - paint
4. Will accept
5. Spoke
6. Were
7. Will you be
8. Were - would all die
9. Don’t see
10. Wouldn’t do - were
11. Had missed - would have been
12. Would’ve been - had walked
13. Had had - would have sent 
14. Were - would call - talk
15. Refused - would have