Answer the following question: Fact 1: Mammals conserve body heat with their hair or fur. Fact 2: Hair and feathers are both made of keratin. Given the two facts above, what do mammals use to conserve body heat?

Pick your answer from:
+ four limbs.
+ Energy..
+ energy.
+ sarcasm.
+ skin.
+ keratin.
+ sawdust.
+ groceries.
Answer:
keratin