Rohan’s mother is . . . . . . . . teacher. A. a B. an C. the D. no article

The correct answer is D. no article.

The article “a” or “an” is used before a singular common noun that refers to a general or unspecified person, place, thing, or idea. In this case, Rohan’s mother is a specific person, so we do not use an article.

The article “the” is used before a singular common noun that refers to a specific person, place, thing, or idea that has already been mentioned or is known to the listener or reader. In this case, Rohan’s mother has not been mentioned before, so we do not use the article “the.”

There is no article before a singular common noun that refers to a general or unspecified person, place, thing, or idea. In this case, Rohan’s mother is a specific person, so we do not use an article.