Brian's mom was watching him play basketball and noticed, for the first time, that he has significant hair in his armpits now. she knows this means brian is:

This means that Brian is starting puberty.  Puberty usually starts between ages 12-16 for boys. Armpit hair, along with body odor and mild acne are a result of DHEA hormone production. This ordinary body process during teenage years that is related to puberty  is called adrenarche.

answer; sensory craving;