Final answer:
Lava flows are correctly described as often being basalt or rhyolite and are extrusive igneous rocks, meaning options A and C are correct. Granite and gabbro, however, are examples of intrusive igneous rocks, making options B and D incorrect for lava flows.
Step-by-step explanation:
Lava flows are associated with extrusive igneous rocks, which are rocks that form from cooled and solidified lava on the earth's surface. The two types of lava flows mentioned in the question, basalt, and rhyolite, are indeed examples of extrusive igneous rocks. Basalt is typically a dark-colored, fine-grained rock that is rich in iron and magnesium.
Rhyolite, on the other hand, is lighter in color and very finely crystalline due to the rapid cooling of high-viscosity lava. The answer to the question would thus include A: often basalt or rhyolite, as both of these are types of lava flows, and C: they are both extrusive igneous rocks.
Conversely, both granite and gabbro are types of intrusive igneous rocks, which means they form from magma that cools and solidifies beneath the surface of the Earth, leading to larger crystal sizes due to the slower cooling rate. Therefore, B and D are incorrect in the context of lava flows, as lava flows are not granite or gabbro and are not intrusive igneous rocks.