EXERCISE 16: Some of the sentences are incorrect. Pick out the wrong ones and correct the mistakes.
1. Plants would die if they don't get enough water.
2. Everything's been prepared for the project, isn't it?
3. If you see a fire, call the fire department immediately.
4. Your brother never goes out with his friends if he hasn't finished his homework, has he?
5. I believe no one can solve the pollution problem, don't I?
6. There's been a new plan to treat wastewater in the city, hasn't there?
7. If you mixed red and green, you'd get yellow.
8. These are devices to detect any heating problems, aren't these?