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: Physiology
Bohr effect is described as: September 2009 
Select and explain. 
A. Decrease in CO2 affinity of hemoglobin when the pH of blood rises, B. Decrease in CO2 affinity of hemoglobin when the pH of blood falls, C. Decrease in O2 affinity of hemoglobin when the pH of blood rises, D. Decrease in O2 affinity of hemoglobin when the pH of blood falls
D: Decrease in O2 affinity of hemoglobin when the pH of blood falls
Answer: D: Decrease in O2 affinity of hemoglobin when the pH of blood falls 
Explanation: Ans. D: Decrease in O2 affinity of hemoglobin when the pH of blood fallsThe decrease in O2 affinity of hemoglobin when the pH of blood falls is called the Bohr effect and is closely related to the fact that deoxygenated hemoglobin (deoxyhemoglobin) binds H+ more actively than does oxyhemoglobin. The pH of blood falls as its CO, content increases, so that when the PCO2 rises, the curve shifts to the right and the P5,, rises.