Answer:
D. partial pressure of oxygen
Explanation:
Partial pressure refers to the force applied by an individual gas per unit area in a mixture of gases which is measured in mm of Hg. The partial pressure determines the movement of the gas molecule in the system.
In the given scenario, the oxygen transport through the blood along with other gases like carbon dioxide and other minute concentration but the gaseous exchange between the lungs and the blood, between the blood and the tissues depends on the partial pressure of the oxygen. The oxygen moves from the higher pressure to lower pressure therefore partial pressure is the determining factor.
Thus, Option-D is correct.