Correct option is A
Explanation:
· The sentence requires the superlative degree since it compares one person to all others the speaker has met.
· "Healthiest" is the correct superlative form of "healthy."
· "Most healthy" is grammatically possible but less commonly used.
· "Healthier" and "more healthy" are comparative forms, used for comparing two people or things.
Correct sentence: He is the healthiest person I have ever met in life.