Which description best characterizes extrusive igneous rocks?

• A. Intrusive igneous rocks cool slowly underground with large crystals.
• B. Intrusive rocks: Basalt, Andesite; Extrusive: Granite, Diorite.
• C. Intrusive: Granite, Diorite; Extrusive: Basalt, Rhyolite.
• D. Intrusive: Obsidian, Pumice; Extrusive: Granite, Diorite.

Answer: (C)

Extrusive igneous rocks form when magma reaches the surface and cools rapidly, creating fine-grained textures or glass. The correct description matches granite and diorite as intrusive rocks (they form underground, cooling slowly to large crystals) and basalt and rhyolite as extrusive rocks (they form from lava at the surface or near it, cooling quickly to small crystals). The other options mix up where cooling happens or swap rock types between intrusive and extrusive—for example, labeling intrusive rocks as basalts and rhyolites or naming obsidian and pumice as intrusive.