**Core Concept**
L-Dopa is a precursor to dopamine that crosses the blood-brain barrier, used to treat Parkinson's disease. However, its peripheral conversion to dopamine outside the brain by the enzyme dopa decarboxylase (DDC) results in significant side effects. Carbidopa is a peripheral decarboxylase inhibitor that prevents this conversion, thereby increasing the availability of L-Dopa in the central nervous system.

**Why the Correct Answer is Right**
The combination of L-Dopa and carbidopa is a classic example of prodrug therapy, where the addition of carbidopa prevents the peripheral conversion of L-Dopa to dopamine, thereby increasing its bioavailability in the brain. This results in improved efficacy and reduced side effects, including nausea, vomiting, and orthostatic hypotension. The carbidopa-L-Dopa combination effectively inhibits the peripheral decarboxylation of L-Dopa, allowing more L-Dopa to cross the blood-brain barrier and be converted to dopamine within the brain.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not address the specific reason for combining L-Dopa with carbidopa.
**Option B:** This option is incorrect because it implies that carbidopa is used to increase the absorption of L-Dopa, which is not the primary reason for its use.
**Option C:** This option is incorrect because it is not a specific enough answer and does not address the mechanism of action of carbidopa.

**Clinical Pearl / High-Yield Fact**
The combination of L-Dopa and carbidopa is a classic example of prodrug therapy, where the addition of a second drug (carbidopa) enhances the efficacy and reduces the side effects of the first drug (L-Dopa). This concept is essential to understand for postgraduate medical students.

**Correct Answer: C. It inhibits peripheral decarboxylation of L-Dopa, thereby increasing its availability in the brain.**