IV.
1. If the environment doesn't become badly polluted, we won't die soon.
2. No river is longer than the Nile river in the world.
3. We might probably go to the moon for our summer holiday in 2050. 
4. In the future, home robots will be able to do all our homework.
5. If I don't have a quite room, I won't be able to do anything.
6. If we are busy, we won't go to the Cherry blossom festival this Sunday.
7. This is the first time we have visited Ho Chi Minh city.
8. Her father has smoked since his wife died.