This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cellular Pathology, Subject name: Pathology
[{'content': 'Principle of Prussian blue stain: \nSelect and explain. \nA. Ferrous to ferricyanide, B. Ferrocyanide to ferroferric cyanide, C. Ferroferriccyanide to ferrocyanide, D. Ferrocyanide to ferricferrocyanide', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. (b) Ferrocyanide to ferroferric cyanide(Ref: Dacie and Lewis Practical Haematology 11th ed, pg 338)Hemosiderin reacts with potassium ferrocyanide to form a blue compound, ferri ferrocyanide; this reaction is the basis of a positive Prussian-blue (Perls') reaction.", 'role': 'assistant'}]