The Thermodynamics of Oxygen Binding to Hemoglobin Are Highly Ordered

The thermodynamics of oxygen binding to hemoglobin are highly ordered. Which of the following
Reflects the physical characteristics relating the binding of O₂ to hemoglobin?

A) causes a large shift of the surrounding secondary structures leading to decreased affinity of the deoxy subunits for CO₂
B) is cooperative, meaning that after the first O2 binds, the other subunits are more readily oxygenated
C) occurs with equal affinity at all 4 subunits
D) results in a release of the heme from the interior to the exterior of the a-subunits, leading to an increase in O₂ affinity of the b-subunits
E) results in a release of the heme from the interior to the exterior of the b-subunits leading to an increase in O₂ affinity of the a-subunits