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

Fact 2: Lung cancer continues to kill, despite modern therapies.

Given the two facts above, answer the question "What can kill?" with the following options: 
- thoughts
 - Tobacco smoke
 - satisfaction
 - Electric devices
 - flow of electrons
 - taxes
 - animals
 - heat produced


 

  Tobacco smoke       