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': "Russell's body is found in - \nSelect and explain. \nA. WBC, B. RBC, C. Mast cell, D. Plasma cell", 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]