Final answer:
The understood subject in the question is 'tú' (you) and the verb 'participar' is conjugated accordingly.
Step-by-step explanation:
The understood subject in the question is 'tú' (you). The correct conjugation of the verb 'participar' in the present tense for 'tú' is 'participas'.
Roberto: ¿Y tú? ¿No participas en un grupo estudiantil?
Carlos: Sí, participo en el Club Internacional.
Learn more about Spanish verbs