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
Binding of oxygen to myoglobin: 
Select and explain. 
A. Is characterized by the sigmoidal saturation curve, B. Occurs at multiple sites, C. Is characterized by the sigmoid and multiple hyperbolic saturation curve, D. Is characterized by the hyperbolic saturation curve
D: Is characterized by the hyperbolic saturation curve
Answer: D: Is characterized by the hyperbolic saturation curve 
Explanation: Myoglobin molecule contains a single O2 binding site and thus the saturation process is characterized by a simple hyperbolic curve, in contrast to hemoglobin, sigmoid saturation curve of which shows positive cooperativity of multiple oxygen binding sites. Ref: Lippincott's Biochemistry, 5th Ed page 26