**Core Concept**
Narcotic overdose occurs due to the potentiation of opioid receptors, leading to excessive inhibition of the central nervous system (CNS). Narcotic antagonists act by competitively binding to opioid receptors, reversing the effects of narcotics and restoring normal CNS function.

**Why the Correct Answer is Right**
Naloxone is a potent opioid antagonist that selectively binds to μ-opioid receptors, thereby reversing the effects of narcotics such as morphine and heroin. This reversal is rapid and can be life-saving in cases of overdose. Naloxone's mechanism of action involves competitive inhibition of opioid receptors, which is mediated by its high affinity for these receptors.

**Why Each Wrong Option is Incorrect**
**Option A:** Diphenhydramine is an antihistamine that can cause sedation but does not have any opioid antagonist properties. It is not effective in reversing narcotic overdose.
**Option B:** Atropine is an anticholinergic agent that can cause various side effects but does not have any opioid antagonist activity. It is not used to treat narcotic overdose.
**Option D:** Nalorphine is a mixed agonist-antagonist opioid that can cause analgesia but also has some opioid agonist activity. It is not an effective opioid antagonist and can actually worsen narcotic overdose.

**Clinical Pearl / High-Yield Fact**
Naloxone is a critical medication in the management of opioid overdose, and its administration can be life-saving. It is essential to note that naloxone's effects are short-lived, requiring repeated doses to maintain reversal of opioid effects.

**✓ Correct Answer: C. Naloxone**