Final answer:
Secondary sex characteristics distinguish males from females by indicating sexual maturity through traits like facial hair in males and development of breasts in females; however, they are not directly involved in reproduction or the onset of menarche.
Step-by-step explanation:
Secondary sex characteristics are important because they help distinguish males from females. These characteristics are the physical signs of sexual maturation that do not directly involve sex organs. Examples of secondary sex characteristics include the development of facial hair and a deepened voice in males, and the development of breasts and hips in females. While they are indicators of sexual maturity, they do not directly participate in the process of reproduction. Therefore, in response to the options provided:
- a. They are not directly involved in reproduction.
- b. They do distinguish males from females.
- c. They do not bring on menarche, as menarche is the onset of menstruation and a direct part of the reproductive cycle.
The correct answer is b. distinguish males from females, since neither menarche nor direct involvement in reproduction is a function of secondary sex characteristics.