present. 1. If my aunt comes to visit, she (give) us a present. 2. If it doesn't rain, we (go) to the beach. 3. If it (snow) tonight, we will make a snowman tomorrow. 4. If you…

Here are the correct forms for the sentences you've provided:

1. If my aunt comes to visit, she will give us a present.
2. If it doesn't rain, we will go to the beach.
3. If it snows tonight, we will make a snowman tomorrow.
4. If you don't try, you will not succeed.
5. If you bring the sandwiches for the picnic, I will bring the drinks.
6. If he talks too long, his parents will not let him use the phone.
7. He will turn on the heater if it gets too cold.
8. You won't understand the questions unless you read the book.
9. If we go to London, we will visit my friend George.
10. If she does well in her exams, my sister will go to university.
11. Jenny will not eat supper if she eats all that ice cream.
12. My brother will drive us to the cinema if we ask him.
13. Uncle Tim will phone us if he wants to come with us.
14. If I knew, I would tell you.
15. If she wants to talk, she will ring up.
16. If he has enough money, he will buy a large house.
17. She will feel lonely if Peter goes away.
18. We will be pleased to see you if you arrive.
19. If we can come on Sunday, we will come.
20. I will understand Mr. Smith if he speaks slowly.

Feel free to ask if you need further clarification or assistance!