Which of the Following Statements Relate to the HbO₂ equilibrium

Which of the following statements relate to the HbO₂ equilibrium curve?
I.Large PO₂ changes cause small to minimal changes in oxygen content, especially at the extreme flat right end (60 to 100 mm Hg) .
II.Small PO₂ changes cause large blood oxygen content changes in the middle, steep portion of the curve (20 to 60 mm Hg) .
III.Large PO₂ changes cause large changes in oxygen content at the extreme flatter ends of the curve, especially the flat right end (60 to 100 mm Hg) .
IV.Small PO₂ changes cause small blood oxygen content changes in the middle, steep portion of the curve (20 to 60 mm Hg) .

A) I, II
B) I, II, III, IV
C) II, III
D) I, II, III