What does the sigmoidal shape of hemoglobin's oxygen binding curve indicate about its cooperativity?

• A. Hemoglobin binds oxygen sequentially without cooperativity.
• B. Hemoglobin exhibits positive cooperativity, enhancing oxygen binding.
• C. Hemoglobin binds oxygen independently without cooperativity.
• D. Hemoglobin exhibits negative cooperativity, reducing oxygen binding.

Answer: (B)