CO2 and 2,3-BPG effect the ability of hemoglobin to bind oxygen. Which statement is true?

a. Stripped Hb cannot bind CO2 or 2,3-BPG.
b. If stripped Hb is treated with 2,3-BPG and CO2, the O2-binding curve for Hb will mirror that of fully intact Hb.
c. If stripped Hb is treated with 2,3-BPG, the O2-binding curve for Hb will shift left.
d. If stripped Hb is treated with CO2, the O2-binding curve for Hb will match the binding curve for Hb with 2,3-BPG