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': 'Hypovitaminosis - D causes - \nSelect and explain. \nA. Zonular cataract, B. Blue - Dot cataract, C. Rosette cataract, D. Cupliform cataract', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Zonular or lamellar cataract is a congenital type Etiology may be either genetic or environmental in origin. Environmental form is associated with: deficiencyof vitamin D hypocalcemia Sometimes maternal rubella infection contracted between 7th and 8th week of gestation may also cause lamellar cataract.', 'role': 'assistant'}]