Hi there!
Answer: C. it's a pronoun that functions as the subject of a sentence or clause.
Explanation: Subjective pronoun can be used as the subject of a sentence. For example: She takes make classes.
first person: singular: I
first person: plural: we
second person: singular: you
second person: plural: you
third person: singular: he, she, it
third person: plural: they
Hope this helps!
-Charlie