People need to breathe. If they don't breathe, they (1)............ die.

Read and choose the best answers.

People need to breathe. If they don't breathe, they (1)............ die. But how to clean the air people breathe? If they breathe (2)............ air, they will have breathe problems and become (3)........... Plants and animals need clean air, too. A lot of things in our lives create harmful gases and (4)............. the air dirty like cars, motorbikes and factories. Dirty air is called polluted air.