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: Pathology
[{'content': 'Acid mucin is best demonstrated by the stain ? \nSelect and explain. \nA. Alcian blue, B. Periodic Acid Schiff (P.A.S.), C. Van Gieson, D. Reticulin', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e. Alacine blue", 'role': 'assistant'}]