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

Fact 2: Incinerated mercury pollutes the air.

Given the two facts above, answer the question "What harms the respiratory and circulatory systems?" with the following options: 
- Greenhouse gasses
 - burning coal
 - inoculation
 - incinerated mercury
 - fossil fuels
 - water vapor
 - Sulfur dioxide
 - air


 

    incinerated mercury     