Concept:High temperature inside the Earth creates geothermal activity, which can form surface features like geysers.Explanation:Underground water that comes into contact with hot rocks or magma gets heated intensely.Heated water builds up pressure and may burst out through openings as steam and hot water.Such an eruption is called a geyser.Fold mountains, horsts, and rift valleys are caused by tectonic movements, not by internal heat.Answer:C. Geyser