Sorry to ask such an obvious question, but this escapes me.
Wheelock’s Chapter 32 SA #4: Plus novisti quid faciendum sit. What use of the subjunctive might this be with the future passive participle. Is this a subjunctive passive periphrastic construction? thanks.
quid faciendum sit – this is subjunctive because it’s an indirect question. It’s what Allen & Greenough call the “second periphrastic conjugation”–a form of esse + gerundive (or “future passive participle”; here neuter because impersonal), implying obligation or necessity.