Answer:
"The program was written by Sara, who is an expert in her field."
"To whom should I talk to about the report?"
Explanation:
Who is a pronoun that represents the subject of a sentence:
Who would like to go to the supermarket?
Who built that castle?
Whom is a pronoun that represents the object of either a verb or a preposition:
To whom was the song dedicated?
Whom do you trust?
I am not sure with whom I will go to the concert.
