If something that can be auburn is a fiber found only in mammals, then what is a fiber found only in mammals?

Answer choices:
- Something that can be auburn
 - They have thick fur
 - Something that is self-aware
 - with their fur
 - To keep their body heat.
 - it helps plants in growing
 - it keeps an organism warm
 - Something that comes in a bundle of fibers

 

 Something that can be auburn         