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': 'Corneal dystrophies are \nSelect and explain. \nA. Primary & unilateral, B. Primary & bilateral, C. Primary, bilateral with systemic disease, D. Primary, unilateral without systemic disease', 'role': 'user'}, {'content': 'Answer: B \nExplanation: B i.e. Primary & bilateral', 'role': 'assistant'}]