This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Biochemistry
Which type of hemoglobin is not normally found within human erythrocytes? 
Select and explain. 
A. HbA, B. HbA2, C. HbCO, D. HbO2
C: HbCO
Answer: C: HbCO 
Explanation: Adult erythrocytes normally do not contain any carboxyhemoglobin, which is formed when hemoglobin binds carbon monoxide. Ref : Biochemistry by U. Satyanarayana 3rd edition Pgno : 206