Answer:
d. A change in the pH
Step-by-step explanation:
Enzymes are defined as biocatalysts that increase the rate of the reactions by decreasing activation energy for those reactions. Most of the enzymes are protein molecules, made up of polymerization of amino acids.
Function of proteins depends on their primary sequence and proper folding. Protein molecules get denatured in unfavorable conditions and they lost their function.
As enzymes are also proteins, change in pH and temperature lead to denaturation of enzyme molecules by changing their active sites (sites where substrate binds).
Hence, from given conditions, change in pH would most affect the ability of enzymes to catalyze a reaction.
Thus, the correct answer is option (d).