**Core Concept**
Non-competitive inhibition is a type of enzyme inhibition where the inhibitor binds to a region of the enzyme outside of the active site, altering the enzyme's shape and reducing its activity. This type of inhibition does not compete with the substrate for the active site, hence the name.

**Why the Correct Answer is Right**
In non-competitive inhibition, the inhibitor binds to a site on the enzyme called the allosteric site, which is distinct from the active site where the substrate binds. This binding causes a conformational change in the enzyme, reducing its ability to bind to the substrate and resulting in a decrease in enzyme activity. The inhibitor does not compete with the substrate for the active site, but rather alters the enzyme's shape, making it less effective at binding to the substrate.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because non-competitive inhibition does not involve the inhibitor competing with the substrate for the active site.
**Option B:** This option is incorrect because non-competitive inhibition involves the inhibitor binding to an allosteric site, not the active site.
**Option C:** This option is incorrect because non-competitive inhibition does not result in a decrease in the K_m (Michaelis constant) of the enzyme.

**Clinical Pearl / High-Yield Fact**
Non-competitive inhibition is often seen with feedback inhibition, where the product of an enzyme-catalyzed reaction inhibits the enzyme that produced it, regulating the reaction and preventing excessive production of the product.

**Correct Answer: C. Non-competitive inhibition does not affect the K_m of the enzyme.