Cow is . . . . . . . . useful animal. A. a B. an C. the D. none of the above

The correct answer is: A. a

Cows are useful animals because they provide us with milk, meat, and leather. They are also used to help plow fields and produce manure, which can be used as fertilizer.

The article “a” is used before singular nouns that do not begin with a vowel sound. The article “an” is used before singular nouns that begin with a vowel sound. The article “the” is used before specific nouns that have already been mentioned or that are unique. The article “none of the above” is used when none of the given options are correct.

In this case, the noun “cow” is singular and begins with a consonant sound, so the article “a” is used.