Fact 1: Lung cancer is most often caused by exposure to tobacco smoke.

Fact 2: Tobacco is smoked in pipes or in cigarettes or bidis.

Given the two facts above, answer the question "what causes lung cancer?" with the following options: 
- Pollution
 - smoking salmon
 - burning
 - cigarettes
 - gasoline
 - lung tissue
 - heating liquids
 - respiration


 

    cigarettes     