1. you … recycle aluminium cans. 2. you …adopt any animal in our zoo. 3. people … throw away litter in the park. 4. humans … cut down forest to clean places for building. 5. we… reduce our oil consumption. 6. people … know more about genetically modified products. 7. authorities … organize environmental campaign
2 can't
3 shouln't
4 have to
5 must/ should
6 should
7should