Fact 1: Smoking causes direct damage to the lungs.

Fact 2: Many people smoke cigarettes.

Given the two facts above, answer the question "what causes direct damage to the lungs?" with the following options: 
- cigarettes
 - burning
 - tissue
 - hypothyroidism
 - breathing
 - hydrogen
 - amoebae
 - influenza


 

 cigarettes        