I believe that the answer is nos caimos
The answer is (acabe) because it refers to the fact that he has not finished his studies and when he finishes it he could finally be an astronaut.
A nosotros no nos importa el itinerario.
answer is nos
E.Poner la nevera en la cocina fácilmente= we could put the fridge in the kitchen easily(the rest options say the bathroom,hallway,food)
