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

Fact 2: Smoke Tobacco smoke , whether directly or passively inhaled, has been shown to worsen asthma.

Given the two facts above, answer the question "What can be caused by direct or passive inhalation?" with the following options: 
- skin grafts
 - prolonged thirst
 - science
 - Toxicity
 - lung cancer
 - negative
 - friction
 - craters


 

     lung cancer    