Why Are Breast Development, Deepening of the Voice, Growth of Body

Why are breast development, deepening of the voice, growth of body hair, and changes in the skin all considered secondary sex characteristics?

A) Because they happen after the maturation of the ovaries and testes.
B) Because they indicate physical maturation but are not directly related to fertility.
C) Because they are not important changes.
D) Because they happen at the end of puberty.