All four of the following statements are factually correct, but which statement best describes sex over the entire life course?A.In the United States, most young men and women become sexually active by the time they reach age seventeen.B.In the United States, most adults are sexually active, but sexual activity among adults declines as they get older, especially after people reach the age of sixty.C.By the time they reach their mid-twenties, more than 90 percent of both women and men reported being sexually active with a partner at least once during the past year.D.By their mid-twenties, about 90 percent of men and women report being sexually active with at least one partner within the past year.

To determine which statement best describes sex over the entire life course, let's analyze each statement step by step:

A. In the United States, most young men and women become sexually active by the time they reach age seventeen.

• This statement focuses on the onset of sexual activity in adolescence. It provides information about when most young people start being sexually active but does not cover the entire life course.

B. In the United States, most adults are sexually active, but sexual activity among adults declines as they get older, especially after people reach the age of sixty.

• This statement provides a broader view of sexual activity over the life course. It mentions that most adults are sexually active and acknowledges a decline in sexual activity as people age, particularly after sixty. This statement covers a wider age range and the changes in sexual activity over time.

C. By the time they reach their mid-twenties, more than 90 percent of both women and men reported being sexually active with a partner at least once during the past year.

• This statement focuses on sexual activity in the mid-twenties. It provides specific data for a particular age group but does not address sexual activity beyond this period.

D. By their mid-twenties, about 90 percent of men and women report being sexually active with at least one partner within the past year.

• Similar to statement C, this statement focuses on the mid-twenties and provides specific data for that age group. It does not cover the entire life course.

Given the analysis, statement B best describes sex over the entire life course. It provides information about sexual activity in adulthood and acknowledges the decline in sexual activity as people age, especially after sixty, thus covering a broader span of the life course.