The correct answer is b) increase in hydrogen ions.
A rightward shift of the oxygen-hemoglobin dissociation curve indicates that hemoglobin has a decreased affinity for oxygen. This usually occurs in response to increased levels of carbon dioxide (CO2) or increased temperature, both of which can lead to increased concentrations of hydrogen ions (H+) in the blood.
When CO2 levels rise, it is converted to carbonic acid in the blood, which then dissociates into bicarbonate and hydrogen ions. The increase in hydrogen ions results in a lower pH, causing acidosis. Therefore, a rightward shift in the curve signifies that hemoglobin is more willing to release oxygen to the tissues, but it simultaneously indicates that the environment is more acidic due to the increased hydrogen ion concentration.
In summary, when the oxygen hemoglobin dissociation curve shifts to the right, it reflects a physiological state that involves an increase in hydrogen ion levels, contributing to changes in blood pH.