Rule reminder
Concessive conjunctions (sebbene, benché, nonostante, malgrado, per quanto, quantunque) always require the subjunctive in the clause they introduce, regardless of the tense of the main verb. They express a contrast or concession ('although', 'even though', 'despite').
Although the project is expensive, the board approved it. Choose the correct form: 'Sebbene il progetto _____ costoso, il consiglio lo ha approvato.'