This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory System Pa 1, Subject name: Physiology
Which of the following oxygen-hemoglobin dissociation curves corresponds to blood during resting (dark purple line) and during exercise ( light purple line) ? 
Select and explain. 
A. D, B. A, C. B, D. C
C: B
Answer: C: B 
Explanation: Factors that shift the oxygen-hemoglobin dissociation curve to the right are: | CO2 released from the muscle tissue, | H+concentration in the muscle capillary blood, | Temperature resulting from heat generated by the exercising muscle. The right shift of the oxygen-hemoglobin curve allows more oxygen to be released to the muscle at a given Po2 in the blood.