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

Fact 2: Many carcinogens are capable of causing gene mutations.

Given the two facts above, answer the question "What can lead to cancer in genes that control the cell cycle?" with the following options: 
- radiation
 - adding heat
 - competition
 - ice
 - bacteria
 - air
 - carcinogens
 - Smoking


 

       carcinogens  