Ответ:
1. If I see John, I will tell him your news.
2. He will be very pleased if it is really true.
3. If you go to town on Monday, you will meet my brother Tom.
4. If you need help, my father will help you.
5. We will have a picnic lunch if the day is fine.
6. If you ask a policeman, he will tell you the way.
7. I will finish the job tomorrow if I can.
8. I will not require an umbrella if it doesn’t rain.
9. If she thinks it over carefully, she will form a clear opinion.
10. If they catch the bus now, they will arrive at half past nine.
11. He will find the answers if he looks at the back of the book.
12. If you want me to, I will come for a walk with you.
13. If he writes to her, she will answer at once.
14. If you wait a few moments, the waiter will bring your coffee.
15. He will lose weight if he stops eating too much.
16. If she is patient, I will try to explain.
17. I will wear a purle tie only if I must.
18. If we leave at once, we will catch the early train.
19. If he does that again, his father will punish him.
20. If she drinks this medicine, she will feel much better.
Надеюсь поможет!