Harrison is 15 years old and has gained both height and weight, some body hair, and a deeper voice during the past year. These changes are examples of:

secondary sex characteristics

Explanation:

A human has two sexual characteristics primary and secondary.

The primary characteristics are sex chromosomes, gonads, level of sex hormones, anatomy of internal genitalia and anatomy of external genitalia. They are present at birth.

The secondary sex characteristics are breasts, menstrual cycle and accumulation of fat in certain parts of the body which gives rise to the hourglass body form for women.

For men they develop a deeper voice, increase in height and weight.

Pubic hair grows in both sexes.

They develop when a person attains puberty.

Hence, Harrison's secondary sex characteristics were developed.