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': 'Volume of an adult eyeball is: \nSelect and explain. \nA. 7.5 mL, B. 6.5 mL, C. 5.5 mL, D. 8 mL', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. 6.5 mL', 'role': 'assistant'}]