What is the other name of dirty air

Choose the letter A, B, C or D to answer these following questions

People need to breathe. If they don’t breathe, they will die. But how clean is the air people breathe? If they breathe dirty air, they will have breathing problems. Plants and animals need fresh air too. A lot of the things in our lives create harmful gases and make the air dirty, like cars, motorbikes, and factories. Dirty air is called polluted air. Air pollution can also make our Earth warmer.

Question: What is the other name of dirty air?