Fact 1: Air pollution harms the respiratory and circulatory systems.

Fact 2: An example of an air pollution reaction is the production of photochemical smog.

Given the two facts above, answer the question "What affects the respiratory and circulatory systems in the body?" with the following options: 
- HIV
 - sulfur
 - smog
 - stress
 - fever
 - sweat
 - heat
 - tar


 

   smog      