## Core Concept
Benzodiazepines act on the **GABA_A receptor**, enhancing the effect of the neurotransmitter gamma-aminobutyric acid (GABA) to produce sedative, hypnotic, anxiolytic, anticonvulsant, and muscle relaxant properties. A benzodiazepine antagonist would counteract these effects by blocking the action of benzodiazepines at the GABA_A receptor.

## Why the Correct Answer is Right
The correct answer, **Flumazenil**, is a specific benzodiazepine receptor antagonist used to treat benzodiazepine overdoses and to reverse sedation after medical procedures. It works by competitively inhibiting the activity at the benzodiazepine recognition site on the GABA/benzodiazepine receptor complex, thereby reversing the sedative effects of benzodiazepines.

## Why Each Wrong Option is Incorrect
* **Option A:** is incorrect because it does not correspond to a recognized benzodiazepine antagonist.
* **Option B:** is incorrect because, like Option A, it does not match a known benzodiazepine antagonist.
* **Option C:** is incorrect as it is not identified as a benzodiazepine antagonist.

## Clinical Pearl / High-Yield Fact
A key clinical point to remember is that **Flumazenil** can precipitate seizures, especially in patients who are physically dependent on benzodiazepines or have ingested a large dose of a benzodiazepine along with other seizure-inducing substances. Its use should be approached with caution.

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