You are answering a USMLE-style medical question. Question: A 62-year-old woman presents to the emergency department for vision changes. About 90 minutes ago she was on the couch watching television with her husband when she suddenly noticed that she couldn't see the screen normally. She also felt a little dizzy. She has never had anything like this happen before. Her general physical exam is unremarkable. Her neurologic exam is notable for loss of vision in the right visual field of both eyes with macular sparing, though extraocular movements are intact. A computed tomography (CT) scan of the head shows no acute intracranial process. Angiography of the brain will most likely show a lesion in which of the following vessels? Options: A) Internal carotid artery B) Anterior cerebral artery C) Posterior cerebral artery D) Basilar artery Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.