Fact 1: Hair is a fiber that is found only in mammals.

Fact 2: Animals can be classified into mammals, reptiles, birds.

Given the two facts above, answer the question "What is a fiber that is not found in reptiles or birds?" with the following options: 
- Tail
 - muscle
 - feathers
 - sugar
 - down
 - hair
 - Fat
 - scales


 

      hair   