Fact 1: Smoking causes direct damage to the lungs.

Fact 2: Smoking causes irreversible lung damage by breaking the air sacs within the lungs.

Given the two facts above, answer the question "What damages air sacs?" with the following options: 
- burning
 - coal
 - Oxygen delivered through cannulas
 - Smoking
 - Drinking alcohol
 - influenza
 - bacteria
 - Cardiovascular exercises


 

    Smoking     