Final answer:
The correct answer to the question from the National Health and Social Life Survey (NHSLS) regarding the marital status of its participants is c) The marital status varied.
Step-by-step explanation:
This survey was conducted to understand the sexual practices of American adults and included persons with different marital statuses, not just a single category. Mention of the NHSLS can be confused with the National Survey of Sexual Health and Behavior (NSSHB), but they are different surveys.
The NSSHB from 2010 has findings like married couples in their 30s having sex more frequently compared to singles, with 27 percent having sex at least twice a week. Whereas the NHSLS would have surveyed a variety of marital statuses to gain a comprehensive understanding of the sexual behaviors among American adults.