This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Lens, Subject name: Ophthalmology
[{'content': 'Which morphological type of cataract is most visually handicapping? \nSelect and explain. \nA. Coical, B. Nuclear, C. Posterior subcapsular, D. Zonular', 'role': 'user'}, {'content': "Answer: C \nExplanation: Cupuliform (Posterior subcapsular) cataract lies right in the pathway of the asil rays and thus causes an early loss of visual acuity. Ref: Parson's 21st/e p.258, 260; Khurana 7th/e p.194 & 4th/e p.177.", 'role': 'assistant'}]