Some animals' fur grows thicker for staying warm in the winter, and mammals have hair and fur. Given these facts, why do some animals have hair that grows longer during the winter among the following options:
- It expands
 - to make braids
 - to wear a scarf
 - to attract mates
 - When it's cold
 - to stay warm
 - It remains dormant
 - genetic diversity


 

      to stay warm   