2. “ Air pollution is a serious problem”

->the scientist said air pollution was  a serious problem…………………………………………….

3. We should learn a foreign language

-> A foreign language should be learnt.…………………………………………….

4. People must protect our environment

-> Our environment must be protected……………………………………..
5. Go out now or you will be punished

-> If you don't go out, you will be punished………………………………………………………….

6 We use a lot of fertilizers. Our environment is polluted

If we used a lot of fertilizers, Our environment would be polluted………………………………………………………….