The is called:

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. 
"The" is a definite article. "The" transpires when we talk about a particular thing. Eg. The food that we ate was delicious. Similarly," The" is also used for some proper nouns. Example- The Red Sea, The Nile. Moreover, "The" also applies to things that are only one of a kind. E.g., The Earth, The Sun. 
"A" and "An" are considered Indefinite articles. Therefore, Option B is incorrect. Option C is inaccurate because action words or doing words are called verbs, not articles.