What does the term "secondary sexual characteristics" refer to?

The term "secondary sexual characteristics" refers to features that emerge and become pronounced during puberty, distinguishing males from females. These characteristics are not present at birth but develop as a result of hormonal changes that occur during adolescence. For example, in males, secondary sexual characteristics may include deeper voice, facial hair, and increased muscle mass, while females may develop features such as breast development and a wider pelvis. This differentiation plays a crucial role in sexual reproduction and signaling maturity to potential mates.

Other options do not accurately describe secondary sexual characteristics. Features that are present at birth pertain to primary sexual characteristics, such as reproductive organs. Traits regulated by the immune system and functions related to metabolism do not pertain to sexual differentiation and maturation, making them irrelevant in the context of secondary sexual characteristics.