Rule reminder
When a direct object pronoun precedes the auxiliary in passato prossimo, the past participle must agree in gender and number with that pronoun. lo→dato, la→data, li→dati, le→date. With 'ne' (quantitative), agreement is also required with the implied noun.
Which is CORRECT? 'You (sg.) gave some to us' (dei biscotti — masc. pl., ne)?