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': 'Fontana-Masson stain mainly stains   what granules  in the  cytoplasm \nSelect and explain. \nA. Melanin, B. Copper, C. Ferritin, D. Hemoglobin', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Fontana masson\xa0 stains\xa0 mainly used to detect melanin granules in cytoplasm of tumour cells\xa0 of melanoma.', 'role': 'assistant'}]