It depends if you they like the party’s or not but since s it’s in ellos(them) form it would be this:
no,no les gustan las fiestas
no they do not like party’s ^
si,les gustan los fiestas
yes,they do like party’s ^
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.
The second one for sure :)
