Decide si se necesita el indicativo o el subjetivo en la siguiente oracion.
necesitan que tu (deshacer) lo que hiciste.

Subjuntivo

Necesitan que tú deshagas lo que hiciste.

They need you to undo what you did.

Explanation: The subjunctive (deshagas) is found in the subordinate clause of sentences that contain a change of subject from the main clause to the subordinate clause. "Ellos necesitan" subject = "Ellos" ; "que tú deshagas" subject = "tú". (There is a change of subject.)

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?

i got it here  

fill in the blank with the correct answer. carlos and sofia and from toa baja to travel west along the coast.