This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Optics and refraction, Subject name: Ophthalmology
[{'content': 'Centre of biconvex lens is called - \nSelect and explain. \nA. Focal point, B. Optical center, C. Epicentre, D. Focal Distance', 'role': 'user'}, {'content': 'Answer: B \nExplanation: optical center is the point in the principal axis of a lens through which light passes without undergoing any detion. It is in the center of lens. Reference : AK khurana 7th edition', 'role': 'assistant'}]