Complete the sentences with the appropriate modal verbs: have to, must, should not, can, should, could, mustn't.
1. We recycle things to get rid of garbage.
2. One ton of recycled paper ... save 17 trees.
3. People ... protect all the forests as they are keys to our survival.
4. We ... be interested in saving more animals.
5. People ... kill the African elephant for its tusks.
6. Eco-friendly people ... keep the environment clean.
7. You ... turn up the heating all the time to reduce the use of energy.
2. One ton of recycled paper can save 17 trees.
3. People have to protect all the forests as they are keys to our survival.
4. We should be interested in saving more animals.
5. People shouldn’t kill the African elephant for its tusks.
6. Eco-friendly people must keep the environment clean.
7. You mustn’t turn up the heating all the time to reduce the use of energy