It’s going to be - C. A subordinate clause that has been written and punctuated as a stand-alone sentence but does not make sense as a sentence.
Why? It is a fragment. That means it is like a piece of a puzzle and without the whole puzzle put together, it just, doesn’t make sense.
Examples - gets in the car. Because you are not going. If u don’t understand, copy and paste this link and watch this video:) hope this helps you. https://www.khanacademy.org/humanities/grammar/syntax-conventions-of-standard-english/fragments-and-run-ons/v/recognizing-fragments-syntax-khan-academy
A pronoun is a word used to stand for (or take the place of) a noun. A pronoun should refer clearly to one, clear, unmistakable noun coming before the pronoun. This noun is called the pronoun's antecedent.