The correct answer is Flumazenil.

- Benzodiazepines exert their effects by enhancing the action of gamma-aminobutyric acid (GABA) at the GABA-A receptor, producing sedation, anxiolysis, muscle relaxation, and anticonvulsant effects.
- In cases of benzodiazepine overdose, patients may present with symptoms such as excessive sedation, respiratory depression, and impaired consciousness.

- Flumazenil is a specific benzodiazepine receptor antagonist that competitively binds to the GABA-A receptor at the benzodiazepine binding site.
- By doing so, it effectively reverses the sedative and CNS depressant effects of benzodiazepines, making it the antidote of choice in benzodiazepine overdose.

It is important to note that Flumazenil should be used cautiously, as it may precipitate withdrawal and seizures in patients with chronic benzodiazepine use or those who have co-ingested proconvulsant substances.

Other agents listed are incorrect for this indication:
- Naloxone is an opioid antagonist used to reverse opioid overdose.
- Physostigmine is an acetylcholinesterase inhibitor used primarily in anticholinergic toxicity.
- Atropine is an anticholinergic agent used to treat bradycardia and organophosphate poisoning.

Reference: Goodman & Gilman’s The Pharmacological Basis of Therapeutics, 13th Edition, Chapter 22: Central Nervous System Depressants and Muscle Relaxants