Statement I : Low temperature preserves the enzyme in a temporarily inactive state whereas high temperature destroys enzymatic activity because proteins are denatured by heat.

• This statement is true. Low temperatures can slow down enzyme activity but do not typically denature the enzyme, essentially preserving it in an inactive state. High temperatures, on the other hand, can cause the enzyme (which is a protein) to denature, or lose its structure, which leads to a loss of enzymatic activity.

Statement II : When the inhibitor closely resembles the substrate in its molecular structure and inhibits the activity of the enzyme, it is known as a competitive inhibitor.

• This statement is also true. A competitive inhibitor is a substance that binds to the active site of an enzyme, preventing the substrate from binding and thus inhibiting the enzyme's activity. Because it competes with the substrate for the same active site, a competitive inhibitor often has a structure that closely resembles that of the substrate.

So, the correct answer is :

Option D : Both Statement I and Statement II are true.