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': 'A patient presents with H/o evening halos and occasional headache for some months. His examination shows normal 10P but shallow AC. He is in which stage of glaucoma: \nSelect and explain. \nA. Acute, B. Absolute, C. Prodrome, D. Constant instability', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. Prodrome', 'role': 'assistant'}]