All of the Following Statements About Binding of 2,3-Bisphosphoglycerate to Hemoglobin

All of the following statements about binding of 2,3-bisphosphoglycerate to hemoglobin are correct EXCEPT

A) one BPG binds to each oxygenated subunit of hemoglobin.
B) promotes release of oxygen from hemoglobin.
C) increased levels in the red blood cells are part of the adaptive reaction to high altitudes.
D) binds less tightly to fetal hemoglobin.
E) causes increased ionic bonding between subunits.