Which of the following examples of igneous rock is extrusive?

Igneous rocks are formed from the solidification of magma or lava. Depending on where the rock cools and solidifies, it can be classified as either extrusive or intrusive. Extrusive rocks are formed when lava from a volcanic eruption cools quickly on the surface of the earth, forming small crystals or no crystals at all. On the other hand, intrusive rocks are formed when magma cools slowly underground, allowing larger crystals to form. Out of the four examples of igneous rock, basalt is the only extrusive rock. Basalt is formed from the rapid cooling of lava on the surface of the earth, resulting in small or no crystals. Granite, gabbro, and diorite, on the other hand, are all intrusive rocks that formed from slow cooling of magma deep within the earth, resulting in larger crystals. Therefore, the correct answer is "Basalt".