Fact 1: Evolution occurs in response to a change in the environment.

Fact 2: Natural selection is the main mechanism of evolution.

Given the two facts above, answer the question "What occurs in response to a change in the environment?" with the following options: 
- relocation
 - sunlight
 - moonlight
 - artificial selection
 - ground to shake
 - Animal survival
 - natural selection
 - It helps them survive


 

       natural selection  