He is ___ one-eyed person.

The correct article is "a" because the choice between "a" and "an" depends on the sound of the word immediately following the article, not its spelling. Although "one" starts with the vowel 'o', it is pronounced with a 'w' sound (like "won"), which is a consonant sound. Therefore, "a" is used before words that begin with a consonant sound.

• "an" is incorrect as it's used before words starting with a vowel sound.
• "the" is a definite article used for specific items, not general ones like "one-eyed person" here.
• "of" is a preposition and grammatically incorrect in this context.