Jeff Is 13 Years Old and He Has Recently Noticed

Multiple Choice

Jeff is 13 years old and he has recently noticed some remarkable changes in himself.Over the past few months his voice has started to change,growing deeper.He has begun to grow pubic hair,as well as the beginnings of a facial beard.He is also filling out,with his muscles developing rapidly.These changes in Jeff are probably due to the action of _____________.

A) gonads
B) thyroid gland
C) pineal gland
D) adrenal gland