As the pH of its surrounding environment decreases from 7.4 to 7.0, protonation of particular _____residues in hemoglobin allows the formation of salt bridges that stabilize the _______state of the quaternary structure, resulting in ______oxygen- binding affinity
a. Asp; R; increased
b. Asp; T, decreased
c. Asp; T, increased
d. His; R; increased
e. His; T; decreased
