Concept:Quartzite, schist, and marble are rocks formed from older rocks changed by heat and pressure.
Explanation:Rocks are grouped into igneous, sedimentary, and metamorphic types.
Metamorphic rocks are produced when existing rocks undergo change due to heat, pressure, or chemical activity.
Quartzite is formed from sandstone.
Schist is formed from shale.
Marble is formed from limestone.
Because all three come from transformation of pre-existing rocks, they belong to the metamorphic group.
Answer:A. Metamorphic