Complete the following passage.

People need to breath. If they don’t breathe, they (1) ____________ die. But how clean is the air people breath? If they breath dirty air, they will have breathing problems and (2) ____________ ill. Plants and animals need clean air, too. (3) ____________ of things in our lives create harmful gases and make the air dirty, like cars, motorbike and factories. Dirty air called (4) ____________ air. Air pollution can also make our earth warmer. The problem of air pollution started with the burning a lot of coal in homes and factories.

Question 4: