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: Orthopaedics
[{'content': 'A patient with pain in back. Lab investigation shows elevated ESR. X-ray skull shows multiple punched out lytic lesions. Most imp. Investigation to be done is - \nSelect and explain. \nA. Serum acid phosphatase, B. CT head with contrast, C. Whole body scan, D. Serum electrophoresis', 'role': 'user'}, {'content': 'Answer: D \nExplanation: This patient has : -\n\nMultiple punched-out lytic lesions of the skull.\nElevated ESR\nBack pain\nDiagnosis is multiple myeloma.\nMultiple myelomas is diagnosed by M bands on serum electrophoresis.', 'role': 'assistant'}]