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: 'Ieri ___ tre riunioni importanti.' (Yesterday, three important meetings were attended.)