Concept:Karst regions show characteristic surface and underground landforms.Explanation:Clints and grikes are surface limestone features.Clints are flat blocks of limestone.Grikes are deep fissures between clints.Stalagmites form inside caves, not on the surface.Cavin is not a standard karst surface landform term.So the correct pair of surface features is clint and grike.Answer:A. i and ii only