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': 'The posterior focal point of the reduced eye situated on the retina is how many millimetre behind the anterior surface of cornea: \nSelect and explain. \nA. 22.9 mm, B. 24.4 mm, C. 23 mm, D. 21 mm', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. 24.4 mm', 'role': 'assistant'}]