ĐK loại 1:
1. If the land isn't polluted, the fammers will be able to grow crops
2. There won't be visual pollution if people don't built too many telephone poles and overhead power lines.
3. If people don't use contaminated water for cooking, their health will not be badly effects.
4. If we don't place dusbins in many places, people will throw rubbish everywhere.
5. If the industrial waste isn't well-treated, the factory won't install a new filtration system.