Answer: B) that.
Explanation: A relative pronoun is a type of pronoun that introduces dependent clauses in sentences (a dependent clause is a phrase that doesn't have complete meaning on its own). They also can stand alone as the subject or object of a sentence. The relative pronouns are who, whoever, whom, whomever, that, which, when, where, and whose. In the given sentence, the relative pronoun is "that" ant it introduces the dependent clause "that was just played."
