Which of the following best describes a person who is very active and healthy?

A person who is very active and healthy can be best described as "vigorous." This term conveys a sense of strength, energy, and vitality, suggesting that the individual possesses both physical stamina and a lively disposition.

In contrast, the other terms do not align with descriptors for someone who is active and healthy. "Indolent" refers to a tendency to avoid activity or exertion, typically implying laziness. "Frailty" indicates weakness or a state of being physically weak, which is the opposite of being active. Lastly, "sluggish" denotes a lack of energy or alertness, often characterized by slow movements or inactivity. Therefore, "vigorous" accurately encapsulates the essence of an active and healthy individual.