Which answer matches this clue: the karst plateau in Friuli-Venezia Giulia that gave the term karst to geology worldwide?

• A Altopiano di Asiago
• B Altopiano delle Murge
• C Carso ✓
• D Altopiano della Sila

The Carso (Kras in Slovenian) is a limestone plateau riddled with caves, sinkholes, and underground rivers; it is the type locality for karst topography.