This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Elementary Optics, Subject name: Ophthalmology
[{'content': 'Maximum contribution to the refractive power of the eye is by: \nSelect and explain. \nA. Anterior surface of cornea, B. Anterior surface of lens, C. Posterior surface of cornea, D. Posterior surface of lens', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. (a) Anterior surface of corneaRef: Cornea by Mannis p. 145On average anterior cornea has refractive power of +48D of convergence and posterior cornea -5D of divergence.', 'role': 'assistant'}]