Final answer:
The subject pronoun that you would use to address your classmate in this context is 'tú' in Spanish.
Step-by-step explanation:
The subject pronoun that you would use to address your classmate in this context is tú. In Spanish, tú is the informal second-person singular pronoun that is used when addressing a single person who is considered a classmate, friend, or someone of a similar age. It is used to refer to someone with whom you have a familiar and informal relationship.
Learn more about Subject pronoun for addressing a classmate in Spanish