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

Fact 2: Lung cancer is the Godzilla of cancers.

Given the two facts above, answer the question "the godzilla of cancers is most often caused by exposure to what?" with the following options: 
- rays or beams
 - fossil fuels
 - Pollution
 - tobacco smoke
 - light energy
 - Chemical energy
 - high temperature
 - harmful substances


 

    tobacco smoke     