detailed solution

Correct option is A

Option A is the correct answer. In simple words, we can say that articles mean the words - A, An, and The. They are placed before a noun to show whether the noun referred to in a sentence is specific or general. "A" and "An" are considered Indefinite articles. "An" is used before nouns in singular numbers that start with vowels{A, E, I, O, U}. It can also occur before countable nouns in the singular number with a vowel sound(Eg. An hour). 
Article "A" takes place with countable nouns in singular numbers that begin with consonants(Eg. A car). 

Option B is incorrect because "The" is a definite article. "The" transpires when we talk about a particular thing. Eg. The cat that scratched me ran away. 

Option C is incorrect because naming words are called nouns.