Hola Carlitos

The question is showing a plural you subject (Juan y tú), this is why we need the "vosotros" form of the verb. I added that note to the hint (that we are referring to "vosotros", not "ustedes") 

Kwiziq is still basing its content (especially questions) on European Spanish. We are soon offering the option to avoid questions using vosotros, for our Latin American Spanish learners, so students will be able to "skip" the questions related to this pronoun that is not used in Latin America. 

Saludos

Inma