Final answer:
Gardening is the most likely leisure activity to be part of the lifestyle of older adults due to its relaxing nature, physical activity, and positive impact on mental well-being.
Step-by-step explanation:
Based on the information provided, the leisure activity that is most likely to be part of the lifestyle of older adults is Gardening. As people age, they often seek activities that are more relaxing and enjoyable. Gardening provides a calm and peaceful experience while allowing older adults to stay physically active and connected to nature. It also offers numerous benefits for mental well-being and can help reduce stress and improve overall cognitive health.