This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Blood Physiology, Subject name: Physiology
[{'content': "HB estimation is not done by \nSelect and explain. \nA. Drabkins method, B. Sahli's method, C. Spectrophotometry, D. Wintrobe method", 'role': 'user'}, {'content': "Answer: D \nExplanation: Some methods of hemoglobin estimation are : Drabkin's method Sahli's method Hemoglobincyanide (HiCN) Method Blood Gas Analyzer (BGA) Whereas Wintrobe's method and Westergren's method: for ESR determination.", 'role': 'assistant'}]