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 of the following is the least common corneal dystrophy: \nSelect and explain. \nA. Macular dystrophy, B. Lattice type ILattice type III, C. Granular corneal dystrophy, D. All', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. Macular dystrophy', 'role': 'assistant'}]