Bonjour Sarah ! The verb "passer" belongs to this group of verbs that could use either "avoir" or "être" as auxiliary in Le Passé Composé. It depends on the context and the meaning of "passer". You can have a look at our related lesson: https://french.kwiziq.com/revision/grammar/passer-can-be-used-with-avoir-or-etre-in-le-passe-compose-and-changes-meaning I hope that's helpful! À bientôt !