This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Physiology
All of the following lead to increased dissociation of O2 from Hb except 
Select and explain. 
A. HbF, B. Increased CO2, C. Increase H+, D. Increase Temperature
A: HbF
Answer: A: HbF 
Explanation: Fetal hemoglobin or fetal hemoglobin, (also hemoglobin F or HbF) is the main oxygen transpo protein in the human fetus during the last seven months of development in the uterus and in the newborn until roughly 6 months old.Ref: Ganong&;s Review of Medical Physiology; 24th edition; page no:641