What damages air sacs?
burning coal Oxygen delivered through cannulas Smoking Drinking alcohol influenza bacteria Cardiovascular exercises
A B C D E F G H
Smoking causes irreversible lung damage by breaking the air sacs within the lungs.
Smoking causes direct damage to the air sacs. 
What damages air sacs? (A) burning (B) coal (C) Oxygen delivered through cannulas (D) Smoking (E) Drinking alcohol (F) influenza (G) bacteria (H) Cardiovascular exercises