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': "Best diagnostic test for Best's disease is: \nSelect and explain. \nA. Dark adaptation, B. ERG, C. EOG, D. Gonioscopy", 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. EOG', 'role': 'assistant'}]