A relative clause primarily modifies a noun, similar to an adjective.
To address the other options:
- A relative clause does not typically stand alone as a sentence; it usually functions as part of a larger sentence, providing additional information about a noun.
- A relative clause does not begin with a noun; it usually starts with a relative pronoun (like who, whom, whose, which, or that) or a relative adverb (like when or where).
So, the correct answer about the function of a relative clause is that it modifies a noun.