Answer:
The word that is the relative pronoun in the sentence is "whom".
Step-by-step explanation:
In the sentence above, "whom" is the relative pronoun. A relative pronoun is a pronoun that sometimes introduces relative clauses in the senteces. They can also stand alone as the subject or object of the sentence. "Whom" is the object form of "who". As in this case, it is commonly used with prepositions.