Which of the following is an example of an igneous rock?

Granite is an example of an igneous rock because it forms from the slow crystallization of magma beneath the Earth's surface. This process allows large crystals to develop, giving granite its coarse-grained texture, which is distinguishable by its speckled appearance and the presence of minerals such as quartz, feldspar, and mica.

In contrast, the other options represent different types of rocks. Limestone is a sedimentary rock primarily composed of calcium carbonate, often formed from the accumulation of marine organisms. Marble, while a metamorphic rock that originates from limestone under heat and pressure, does not fit the category of igneous rocks. Shale is another type of sedimentary rock formed from compressed mud and clay, lacking any igneous characteristics. Thus, granite is the clear choice as the only igneous rock among the options provided.