This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anatomy, Development and clinical examination, Subject name: Ophthalmology
[{'content': 'The veical diameter of an adult eye is \nSelect and explain. \nA. 7 mm, B. 27 mm, C. 21 mm, D. 23 mm', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Dimensions of an adult eyeball Anteroposterior diameter 24mm Horizontal diameter 23.5mm Veical diameter 23 mm Circumference 75 mm Volume 6.5 ml Weight 7 gm Reference: A.K.Khurana; 6th edition; Page no:3', 'role': 'assistant'}]