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
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: 
Select and explain. 
A. Acute, B. Absolute, C. Prodrome, D. Constant instability
C: Prodrome
Answer: C: Prodrome 
Explanation: Ans. Prodrome