Correct Answer: Frall

Solution : The third option is correct.

Vigorous refers to being full of physical strength, energy, or determination. On the other hand, frail describes something or someone that is physically weak or delicate, lacking in strength and robustness.

The meanings of the other options are as follows:

• Buoyant means cheerful, optimistic, or able to float on water.
• Sturdy means strong and robust in build.
• Robust means strong and healthy, full of vigour and vitality.