12) E

We must first identify the products that will be formed due to the enzyme action.

Carbohydrase will break down carbohydrates to form sugars such as glucose
Protease will break down proteins to form amino acids
Lipase will break down lipids to form fatty acids and glycerol

Sugars such as glucose will not cause a change in pH because it is neither basic nor acidic.
Amino acids have an acidic element to their molecule structure so they will cause the pH to decrease.
Fatty acids will also cause the pH to decrease.

So products of protein and lipid will cause a change in pH.
Hence the answer is E.