Così fan tutte is described as:

• A. A Mozart opera buffa that is philosophically focused on beauty, seduction, and cruel reality; now controversial from a feminist POV
• B. A Mozart opera buffa about loyalty and fidelity
• C. A sacred choral work with incidental scenes
• D. A tragic opera about a noble family's downfall

Answer: (B)

Così fan tutte is a Mozart opera buffa about loyalty and fidelity. It’s a light, comic work in which two young men test the faithfulness of their fiancées through disguises and schemes, exploring how love, trust, and social expectations handle flirtation and temptation. The emphasis is on the humor of the situation and the musicians’ witty portrayal of the characters’ changing affections, rather than on solemn tragedy or sacred ceremony. The description focusing on fidelity captures the core of the plot and the genre, making it the best fit.