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': 'Most common adverse effect of oral contraceptive is: \nSelect and explain. \nA. Colour blindness, B. Optic neuritis, C. Ringscotoma, D. Nystagmus', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. Opticneuritis', 'role': 'assistant'}]