The correct answer is C. The is the definite article. It is used to refer to a specific person, place, thing, or idea that has already been mentioned or is known to the listener or reader.
A is not the definite article. It is an indefinite article. It is used to refer to a general person, place, thing, or idea.
B is not the definite article. It is also an indefinite article. It is used to refer to a general person, place, thing, or idea that begins with a vowel sound.
D is not the correct answer. It is not an article.