Answer:
2) . why didn't you arrive ? You should have been there .
Explanation : Firstly i chose this option cuz it was was asking why didn't u come ? so first ur asking why did she / he not come to the party .
secondly 'you should have been there ' it feels like u r telling that she / he shd have been there cuz everyone was there and all but only she / he weren't there .
hope this helped !