Answer: Ella
Explanation: “Ella” is a subject pronoun meaning she, it is a third person singular pronoun. The conjugation “es” is the third person singular conjugation of the verb “ser”. Additionally, the person in parentheses, La señora Moreno, is a singular female. This means that you would use the subject pronoun “she” or “ella” as a substitute. Yo means I, and since we are not talking about ourselves, it is incorrect. Ellos refers to they (masculine), and La señora is not plural, nor masculine. This rules out the other two options as well.
