* Diorite is an intrusive igneous rock, meaning it forms when magma cools and solidifies below the Earth's surface.

* Coarse-grained texture indicates that the minerals within the rock had ample time to grow into larger crystals.

Why Slow Cooling Deep Underground?

* Slow cooling allows for the formation of larger crystals. The longer the magma remains below the surface, the more time minerals have to arrange themselves into crystalline structures.

* Deep underground provides the ideal environment for slow cooling. Magma deep within the Earth is insulated by surrounding rock, preventing rapid heat loss.

Other Options and Why They're Incorrect:

* Fast cooling: Rapid cooling results in smaller crystals, forming fine-grained rocks like basalt.

* Above ground: Extrusive rocks like rhyolite form when lava cools quickly at the surface.

* Near a volcano: While diorite can form near volcanoes, the location alone doesn't guarantee slow cooling. The depth and insulation are key.

In summary: Slow cooling deep underground is the perfect combination of factors to produce a coarse-grained intrusive rock like diorite.