The correct answer is A. Their
Explanation:
According to grammar, a pronoun is a word that replaces a noun, this means this word is used to refer to a person, place or thing previously mentioned. In this case, the compound antecedent is "Stacy or Emily" as these are the words before the personal pronoun. Additionally, it is important that the antecedent and the personal pronoun agree in number; therefore if the antecedent is plural the pronoun that refers to it should be equally plural and if the antecedent is singular the pronoun should be singular. Considering this, as the antecedent is "Stacy or Emily" and this is plural as it is referring to two people, the personal pronoun should be plural as well which means the most appropriate option is "their" because this pronoun refers to "they" or "Stacy or Emily" who are the subjects in the sentence.
