I believe that hair and limbs are homology because all mammals have hair and similar limb structure. Hair loss and social behavior on the other hand are homolasy because not all mammals have them. Homology is the similar traits due to common ancestry while homoplasy is similar traits for other reasons other than common ancestry.
The answer is cold blooded animals, like lizards, because they can't control their own body temperature like warm blooded animals, such as a dog or cat, can.
