Fact 1: Mutations that lead to cancer usually occur in genes that control the cell cycle.

Fact 2: Radiation causes mutation.

Given the two facts above, answer the question "What can affect genes that control the cell cycle?" with the following options: 
- Leptospirosis
 - acetic acid
 - water vapor
 - Smoking
 - butter
 - radiation
 - resistance
 - gasoline


 

      radiation   