Final answer:
The correct recommendation for older adults by health care providers, according to HHS guidelines, is to engage in at least a) 150 minutes of moderate intensity physical activity weekly.
Step-by-step explanation:
Health care providers should recommend that older adults engage in at least 150 minutes of moderate intensity physical activity weekly, or 75 minutes of vigorous intensity exercise, preferably spread out over the week. The 2018 Physical Activity Guidelines by the U.S. Department of Health and Human Services (HHS) suggest that adults should move more, sit less, and include a combination of moderate and vigorous activities.
Therefore, among the provided options, A. 150 minutes of moderate intensity physical activity weekly is the correct recommendation for older adults, as this aligns with the HHS guidelines for maintaining health and reducing chronic disease risk.