Final answer:
The subject pronoun to use when talking about Alfredo and Maximiliano is 'ellos'.
Step-by-step explanation:
The correct subject pronoun to use when talking about Alfredo and Maximiliano is ellos. In Spanish, the subject pronouns are used to refer to the person or people performing the action of the verb. The subject pronoun 'ellos' is used when referring to a group of males or a mixed group of males and females. Since Alfredo and Maximiliano are not specified as exclusively female, the pronoun 'ellas' is not correct. 'Nosotros' is the pronoun used to refer to a group that includes the speaker, and 'ustedes' is the pronoun used to address a group of people formally.
Learn more about Subject pronouns in Spanish