*Complete the sentences with the correct prepositions.
6. Leave our electric appliances..................when they are not.........use is a bad habit.
7. It takes many years...........plastic waste to break down.............small pieces.
8. Both students and local people take part..............the event to pick up rubbish.........the central maket.
9. We should set..........more rubbish bins.............public places to keep the environment clean and safe............everyone.