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
HB estimation is not done by 
Select and explain. 
A. Drabkins method, B. Sahli's method, C. Spectrophotometry, D. Wintrobe method
D: Wintrobe method
Answer: D: Wintrobe method 
Explanation: 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.