Select the word that functions as a relative pronoun in the sentence.
my mother is the person that has always believed in me

The relative pronoun in this sentence is 'that.'

Relative pronouns are used to introduce relative clauses. A relative clause is a clause that provides more information about a person, thing, or situation. The most common relative pronouns in the English language are: who, whom, which, that and whose. In the sentence: 'My mother is the person that has always believed in me', relative pronoun 'that' tells us more about the speaker's mother and the nature of their relationship.

[content deleted] - user123802726recklesschicken

the answer is definitely d. sorry for a late response.