Final answer:
Option A). True. Geographic isolation can lead to speciation by causing genetic divergence and the formation of new species.
Step-by-step explanation:
Geographic isolation can indeed be a cause of speciation. When a population of organisms is separated by a physical barrier such as a mountain range or body of water, gene flow between the two populations is reduced or cut off completely. This leads to genetic divergence and eventually the formation of new species. For example, the Galapagos Islands are known for their unique species, such as the Darwin's finches, which evolved through geographic isolation. Therefore, the correct answer is true.