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: Gynaecology & Obstetrics
[{'content': 'For maturity estimation, amniotic fluid cells are stained with : \nSelect and explain. \nA. Nile blue sulphate, B. Methylene blue, C. Mucicarmine, D. Sudan black', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Nile blue sulphate', 'role': 'assistant'}]