You are presented with the question "What affects the respiratory and circulatory systems in the body?" and the following answer choices: 
- HIV
 - sulfur
 - smog
 - stress
 - fever
 - sweat
 - heat
 - tar

Now knowing that air pollution harms the respiratory and circulatory systems and an example of an air pollution reaction is the production of photochemical smog, choose the best answer.


 

   smog      