## Core Concept
Competitive inhibition is a type of enzyme inhibition where a molecule, known as a competitive inhibitor, closely resembles the substrate and competes with it for binding to the active site of the enzyme. This type of inhibition can be overcome by increasing the concentration of the substrate, which effectively outcompetes the inhibitor for the active site.

## Why the Correct Answer is Right
In competitive inhibition, the inhibitor (I) competes with the substrate (S) for the active site of the enzyme (E), forming an enzyme-inhibitor complex (EI) that cannot form product. The presence of the inhibitor increases the Km (Michaelis constant) of the enzyme for the substrate, indicating a decreased affinity of the enzyme for the substrate. However, the Vmax (maximum velocity) of the enzyme remains unchanged because, at sufficiently high substrate concentrations, the substrate can outcompete the inhibitor for the active site. This is why option is correct.

## Why Each Wrong Option is Incorrect
**Option A:** This option might suggest that competitive inhibition decreases Vmax, which is incorrect because, although the inhibitor appears to decrease the enzyme's affinity for the substrate (increasing Km), it does not change the maximum velocity (Vmax) that can be achieved at saturating substrate concentrations.

**Option B:** This option could imply that competitive inhibition is irreversible, which is incorrect. Competitive inhibition is a reversible form of inhibition.

**Option C:** This could suggest that the inhibitor binds to an allosteric site, which is characteristic of allosteric or non-competitive inhibition, not competitive inhibition.

## Clinical Pearl / High-Yield Fact
A key clinical pearl is that competitive inhibitors can be overcome by increasing the substrate concentration. A classic example is the use of probenecid, which competitively inhibits the renal tubular secretion of penicillin, thereby increasing penicillin levels in the blood.

## Correct Answer Line
**Correct Answer: D.**