What type of rock is formed from the cooling and solidification of magma?

The correct answer is that igneous rock is formed from the cooling and solidification of magma. This process occurs when molten rock, known as magma when it's beneath the earth's surface and lava when it is above, cools and crystallizes. The characteristics of an igneous rock depend largely on the rate at which the magma cools; if it cools slowly beneath the surface, it forms intrusive or plutonic igneous rocks, which tend to have larger crystals. Conversely, if it cools quickly on the surface, it forms extrusive or volcanic igneous rocks, which have smaller crystals due to rapid cooling.

This fundamental process distinguishes igneous rocks from the other types listed. Metamorphic rock is formed through the alteration of existing rock types (igneous, sedimentary, or other metamorphic rocks) under heat and pressure without melting. Sedimentary rock is created from the accumulation and lithification of sediment. While volcanic rock is indeed a specific subset of igneous rock formed from lava that cools on the Earth's surface, the broader category of "igneous rock" encompasses both intrusive and extrusive types overall.