Given below are two statements. One is labelled Assertion (A) and the other is labelled Reason (R).
Assertion (A): Competitive inhibitors decrease the activity of enzymes by resembling the substrate's molecular structure.
Reason (R): This similarity allows competitive inhibitors to bind to the enzyme's substrate-binding site, preventing the actual substrate from binding.
In light of the above statements, choose the correct answer from the options given below.

Assertion (A) is correct. Competitive inhibitors are molecules that closely resemble the substrate of an enzyme. They compete with the substrate for binding to the active site of the enzyme. Because they resemble the substrate, they can bind to the active site, but they do not undergo catalysis like the substrate does. As a result, the competitive inhibitor competes with the substrate for binding to the enzyme, reducing the enzyme's activity.

Reason (R) is also correct. Because competitive inhibitors resemble the substrate, they can bind to the same active site on the enzyme that the substrate would normally occupy. Once bound, the competitive inhibitor blocks the substrate from binding to the active site, effectively inhibiting the enzyme's activity. Since the inhibitor and substrate compete for the same binding site, increasing the concentration of substrate can overcome the inhibition caused by competitive inhibitors.

Therefore, Reason (R) provides a valid explanation for why Assertion (A) is true. The similarity between competitive inhibitors and the substrate allows them to bind to the enzyme's active site, interfering with substrate binding and reducing enzyme activity.