the amount of sunlight present the fox's habitat the fox's genes the fox's age
I gave my students this multiple choice question: In the winter, the fur of the arctic fox is white. In summer, the fur darkens to a reddish brown. What most likely causes the fur of the fox to change color?

Only one answer is correct among these 4 choices:
- the amount of sunlight present
- the fox's habitat
- the fox's genes
- the fox's age

Could you tell me which one is correct?

the fox's genes