Final answer:
Men experience a decline in sexual function as they age, while women often face the lack of a partner as their main sexual issue.
Step-by-step explanation:
The correct answer is: a. Men; Women
Physiologically, men experience a gradual decline in sexual function as they age, known as primary aging. This decline in male sexual performance is often medicalized and seen as needing treatment to maintain a sense of youthful masculinity. On the other hand, the main sexual issue for women is often the lack of a partner, as they may experience a sense of relief from the fear of unwanted pregnancy and their children being grown.