Rule reminder
In the past tense (passato prossimo), impersonal si uses 'si e' + past participle. With transitive verbs the participle agrees with the object. With intransitive verbs (and reflexive verbs) the participle is masculine singular. With 'ci si' (reflexive), the participle is masculine plural.
Completa: 'Al ristorante ___ una pizza margherita.' (At the restaurant, a margherita pizza was eaten.)