Ответ:
1. If we don't support the library, it will close.
2. I will make some posters for you, if you need more publicity.
3. Mum and dad will go to the march if it doesn't rain.
4. If we do nothing, things won't change.
5. If the circus comes to town, Tim won't go.
6. If you go to the meeting, you will find out why people are unhappy.