Choose A, B, C or D to complete the following passage

AIR QUALITY

People need to breath. If they don’t breath, they (1)............. die. But how clean is the air people breath?

If they (2)................... dirty air, they will have breathing problems and (3)............. ill. Plants and animals need clean air, too. (4)............. of things in our lives create harmful gases and make the air dirty, like cars, motorbike and factories. Dirty air called (5).............. air. Air pollution can also makes our Earth warmer. The problem of air pollution started with the burning a lot of coal in homes and factories.

(1)...................

• A. 
  will
• B. 
  is
• C. 
  are
• D. 
  be