Ответ:

1. Helen takes the umbrella if it rains.

2. If John know how difficult the exam is, he doesn't take it.

3. If Marry has a country house she takes up gardening

4. Water boils when the temperature is 100 above zero.

5. If a better dress exist Susan buys it for sure

6. If Bob agrees on the subject, he changes his attitude to it.

7. When the night comes, the weather becomes colder