Final answer:
Increased levels of hormones during puberty lead to the development of secondary sex characteristics, which are physical traits distinguishing an individual's sex. These include features such as facial hair and breasts.
Step-by-step explanation:
Secondary Sex Characteristics at Puberty
At puberty, an increased production of hormones results in the development of secondary sex characteristics, the physical traits that identify an individual's sex. These changes include the development of features like facial hair in males due to high levels of testosterone and the development of breasts in females due to high levels of estrogen. Puberty marks a period of rapid body growth and significant changes in body size, composition, and shape, leading to sexual dimorphism. While the timing of puberty can vary greatly due to biological and environmental factors, it typically occurs earlier in females than in males.
The correct answer to the question is: Option 2 - Secondary sex characteristics.