Proteins cannot be denatured by adding

Proteins cannot be denatured by adding water.

Proteins are denatured by treatment with alkaline or acid, oxidizing or reducing agents, certain organic solvents, and also by heating. Denaturing agents are those that affect the secondary and tertiary structures without affecting the primary structure. Thus, we can say that protein can be denatured by the addition of all the other options but water.

Hence, the correct answer is option A) water.