Extrusive (Intrusive) rocks are forms of

Answer: (a) Igneous rocks

Extrusive (volcanic) and intrusive (plutonic) rocks are both igneous.

The idea

Igneous rocks share one origin: cooling and solidification of molten material. Their textures differ with where and how fast that cooling occurs. Location changes the subtype, not the main rock family.

Rock melts to form magma → Magma stays below ground or reaches the surface → Slow underground cooling allows larger crystals → Fast surface cooling gives small crystals or glass → Both routes produce igneous rock

Also know

Granite and basalt are common intrusive and extrusive examples, though they also differ in composition. Gabbro is the coarse-grained compositional counterpart of basalt. Obsidian has a glassy texture and pumice preserves gas bubbles. A sedimentary rock is made from deposits; a metamorphic rock is altered largely without melting.