Fact 1: Coal is used for generating heat by burning.

Fact 2: Coal releases mercury when it is burned.

Given the two facts above, answer the question "What can release mercury into the atmosphere? " with the following options: 
- smoking tobacco
 - hydrogen and oxygen
 - flow of electrons
 - cigarettes
 - chemical reaction
 - an engine
 - generating heat
 - one celled organisms


 

       generating heat  