Which statement correctly classifies intrusive igneous rocks and extrusive igneous rocks?

• A. Intrusive rocks: Granite, Diorite; Extrusive: Basalt, Rhyolite.
• B. Intrusive rocks: Basalt, Andesite; Extrusive: Granite, Diorite.
• C. Intrusive rocks: Obsidian, Pumice; Extrusive: Granite, Diorite.
• D. Intrusive rocks: Sandstone, Limestone; Extrusive: Coal, Chalk.

Answer: (A)

Understanding how rocks are classified as intrusive or extrusive hinges on where the cooling of molten rock occurs and the resulting crystal size. When magma cools slowly underground, crystals have time to grow large, producing coarse-grained rocks like granite and diorite. When magma erupts or comes near the surface and cools rapidly, crystals stay very small or form glass, leading to fine-grained or glassy rocks like basalt and rhyolite. Therefore, granite and diorite are intrusive; basalt and rhyolite are extrusive. This pairing correctly reflects that pattern. Other options mix up the placement or include non-igneous rocks, which don’t fit this classification.