Question

which process is necessary for the formation of an igneous rock? compaction and cementation of sediments. transformation due to heat and pressure. cooling and solidification of molten material. weathering and erosion of existing rock.

Explanation:

Igneous rocks form when molten rock (magma or lava) cools and hardens. Compaction/cementation forms sedimentary rocks, heat/pressure forms metamorphic rocks, and weathering/erosion breaks down existing rocks.

Answer:

Cooling and solidification of molten material.