Bonjour Meghna ! Here we use the "politeness" *vous*, which refers to one person, hence the agreement in the singular masculine form. Have a look at our related lesson on agreement with "être", which explains the case of "vous" in detail: Agreeing past participle with subject's gender and number with (+ être) verbs in the compound past in French (Le Passé Composé) Bonne journée !