This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Ophthalmology
[{'content': 'Sclera a thickest at: \nSelect and explain. \nA. Limbus, B. Inseion of recti, C. Posterior pole, D. Equator', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Posterior pole', 'role': 'assistant'}]