Così fan tutte's core dramatic device involves:

• A. Ferrando and Guglielmo disguising themselves to woo each other's fiancée to test loyalty
• B. A chorus of priests blessing a marriage
• C. A spy thriller set at court
• D. A journey of a knight and a dragon

Answer: (A)

The main concept being tested is how deception and disguise drive the action to probe fidelity and the nature of love. In Così fan tutte the two men, Ferrando and Guglielmo, disguise themselves as strangers (Albanian suitors) and attempt to woo each other’s fiancées to see how loyal the women will be. This use of disguise creates dramatic irony: the audience knows the truth while the characters believe the ruse, so the situations become comic yet revealing of deeper feelings and temptations. The disguises are the engine that propels the plot, generating the misunderstandings, tests of constancy, and eventual moral reflection that shape the opera’s themes. Other options don’t fit this work: there isn’t a priestly blessing in a ceremonial sense, there’s no spy-thriller mood at court, and a knight-and-dragon journey belongs to a very different genre and story. The testing of fidelity through the deliberate deception of the lovers is distinctive and central to how Così unfolds.