In which situation would you most likely use the usted form? con amigos con profesores con niños con compañeros

You would use usted with con profesores because usted is used in formal situations, like talking to a teacher. All of the other options would be a more casual conversation.

Right answer: a. comprarías

this question is given using the conditional form. conditional tenses are is used when talking about hypothetical situations and probabilities. also, this is used when making polite requests. so comprarías is the conjugation of the verb comprar that matches the second person singular in the conditional. finally:

¿cuál comprarías tú?

El saco  de dormir  is the anwser