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': 'Which is the commonest congenital cataract which presents as visual impairment? \nSelect and explain. \nA. Nuclear, B. Zonular, C. Capsular, D. Coralliform', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Lamellar or Zonular cataract refer to the developmental cataract in which the opacity occupies a discrete zone in the lens. It is the most common type of congenital cataract presenting with visual impairment. It is usually bilateral. Typically this cataract occurs in a zone of fetal nucleus surrounding the embryonic nucleus. Ref: Ophthalmology by A K Khurana, 4th edition, Page 172.', 'role': 'assistant'}]