Which statement best contrasts intrusive and extrusive rocks?

• A. Intrusive rocks form at the surface with small crystals.
• B. Extrusive rocks form underground with large crystals.
• C. Intrusive rocks form below the surface with large crystals.
• D. Intrusive rocks form below the surface with large crystals; Extrusive rocks form at the surface with small crystals.

Answer: (D)

Crystals size in igneous rocks reflects cooling rate and where solidification occurs. Intrusive rocks crystallize underground, cooling slowly, which allows crystals to grow large. Extrusive rocks erupt or form at the surface and cool rapidly, producing small crystals. The statement that best contrasts them says intrusive rocks form below the surface with large crystals; extrusive rocks form at the surface with small crystals. Other options misstate one part: intrusive forming at the surface with small crystals would imply rapid cooling, which isn’t correct; extrusive rocks forming underground with large crystals contradicts their surface formation and rapid cooling; and a choice that only mentions intrusive rocks without contrasting the extrusive type doesn’t complete the contrast.