Answer: The correct answer is-
D) a change in shape of the active sites of the enzyme.
Enzymes are primarily protein molecules that drive various chemical reactions ( by increasing the rate of reaction) within the body of living organisms.
Protease is a protein digesting enzyme that works on specific pH ( such as pepsin works on pH 2 within stomach, which is highly acidic) .
Shape of an enzyme determine its function as they have active sites ( which have unique shapes) that fit in the substrate and carry out the chemical reactions.
A major change in pH can alter the shape of the active sites of the enzyme, making it inactive.
Thus, option D) is the right answer.