**Core Concept**
Competitive inhibition is a type of enzyme inhibition where the inhibitor molecule structurally resembles the substrate and competes with the substrate for binding to the active site of the enzyme. This results in a decrease in the enzyme's activity, but the inhibitor's presence does not alter the enzyme's structure.

**Why the Correct Answer is Right**
In competitive inhibition, the inhibitor and substrate compete for the same binding site on the enzyme. This competition results in a decrease in the enzyme's activity, as the substrate is unable to bind to the enzyme due to the presence of the inhibitor. The inhibitor does not alter the enzyme's structure, but rather occupies the active site, preventing the substrate from binding. This type of inhibition can be overcome by increasing the substrate concentration, which allows more substrate molecules to bind to the enzyme, thereby increasing its activity.

**Why Each Wrong Option is Incorrect**
**Option A:** Inhibitors that alter the enzyme's structure are called allosteric inhibitors, not competitive inhibitors.
**Option B:** Non-competitive inhibition results in a decrease in enzyme activity, but the inhibitor does not compete with the substrate for binding to the active site.
**Option C:** Uncompetitive inhibition occurs when the inhibitor binds to the enzyme-substrate complex, resulting in a decrease in enzyme activity.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that competitive inhibition can be overcome by increasing the substrate concentration, which is a key concept in pharmacology and biochemistry.

**Correct Answer: A.**