Final answer:
Men experience gradual fertility decline due to andropause, while women have a marked decrease in fertility leading to menopause, where the ability to conceive ends.
Step-by-step explanation:
The statement about the sexual-reproductive system for both sexes as people age that is true is: the male reproductive system remains relatively unchanged with age. However, this needs clarification. While it is true that men do not experience a sharp transition similar to menopause in women, they do experience gradual changes. Fertility in males tends to decline with age due to a decrease in testosterone levels, known as andropause, but this decline does not completely prevent fertility and often allows men to remain capable of fathering children much longer than women can conceive. In contrast, women experience a more marked decline in fertility, which accelerates after the age of 35, leading up to menopause, the time when menstrual periods cease altogether and the ability to conceive ends.