Answer:
The sentence that uses a relative pronoun correctly is the following one: The green dress is the one that I want.
Explanation:
A relative pronoun introduces dependent clauses in sentences that are called relative clauses. They can also stand alone as the subject or object of the sentence. Without the relative pronoun, the relative clause would not exist. In this case, the relative clause has been introduced by the relative pronoun that and it modifies the noun "one".
