What is the function of the relative pronoun in the adjective clause?
albert einstein, whose theories changed science forever, is a great inspiration to me.
a. possessive
b. subject
c. object of a preposition
d. direct object

The function of the relative pronoun in the adjective clause is A. POSSESSIVE.

In the above sentence:
the adjective clause is whose theories changed science forever.
the relative pronoun in the adjective clause is whose

The relative pronoun whose is a possessive for of who, another relative pronoun.

There are 5 common relative pronouns used in adjective clauses.
These are who, which, that, whose, and whom.

who - refers to people
which - refers to things
that - refers to people or thing
whose - possessive form of who; describes something that belongs to or is part of someone or something mentioned in the main clause.
whom - object form of who; stands for the noun that receives the action of the verb in the adjective clause.

By by showing how hard it was for the sisters to feign grief