Identify the Correct Statement(s) $\mathrm { P } _ { 0 _ { 2 } }$

Identify the correct statement(s) .

A) The presence of hemoglobin keeps the blood $\mathrm { P } _ { 0 _ { 2 } }$ low and favors O₂ movement into the blood, despite a very large transfer of O₂ until hemoglobin is completely saturated.
B) Hemoglobin can combine with O₂, CO₂, H⁺, and CO.
C) Hemoglobin unloads more O₂ in the presence of increased tissue acidity.
D) Hemoglobin buffers against changes in pH due to respiratory carbonic acid.
E) All of these.