Which answer matches this clue: UNESCO-listed Sardinian polyphonic singing where four male voices produce deep guttural overtones?

• A Trallallero
• B Canto a tenore ✓
• C Bella ciao
• D Canto ambrosiano

Canto a tenore features four voices: the bassu and contra for drone and guttural harmonics, and the boghe and mesu boghe for melody.