Select the most appropriate option to fill in the blank and make a grammatically correct sentence.

Anand Kumar is ____ unique teacher.

a

The correct option to fill in the blank is a.

The word "unique" means "being the only one of its kind; unlike anything else." In the context of the sentence, Anand Kumar is a unique teacher because he is the only one who teaches underprivileged children in Bihar for free.

The other options are not as appropriate.

• No article is also grammatically correct, but it sounds a bit informal.
• An is used before singular nouns that begin with a vowel sound. The word "unique" does not begin with a vowel sound, so we cannot use "an".
• The is used before singular nouns that are specific or unique. In the context of the sentence, Anand Kumar is not the only unique teacher in the world, so we cannot use "the".
• A is used before singular nouns that are not specific or unique. In the context of the sentence, Anand Kumar is a unique teacher, but he is not the only one, so we can use "a".