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

Fact 2: Tobacco smoke consists of solid particles and gases.

Given the two facts above, answer the question "What is most often caused by exposure to solid particles and gases?" with the following options: 
- syphilis
 - diabetes
 - contamination
 - scattered light
 - lung cancer
 - hair color
 - global warming
 - Pollution


 

     lung cancer    