Concept:Metamorphic rocks form when existing rocks are changed by heat, pressure, or chemical fluids.Explanation:Granite is an igneous rock formed from cooled magma.Sandstone and shale are sedimentary rocks made from layers of particles.Quartzite is a metamorphic rock that forms when quartz sandstone is subjected to high heat and pressure.The quartz grains recrystallize and bond together, making the rock very hard and resistant to weathering.Other common metamorphic rocks include marble (from limestone) and schist.Answer:B. Quartzite