Answer: The underlined part of the sentence (who purchase parking spots) is a relative clause.
Step-by-step explanation: A relative clause is a dependent clause, that is to say a clause that cannot stand alone as a sentence, which is introduced by a relative pronoun. Moreover, relative clauses provide additional information aout something or someone. In the sentence provided, "who purchase parking spots" is a relative clause because it has been introduced by the relative pronoun "who" and it is adding information about the noun "students". Furthermore, "who purchase parking spots" is a defining relative clause because it has not been separated from the rest of the sentence with commas.