**Core Concept**
The question is testing the knowledge of opioid medications that are available in non-oral formulations, specifically a nasal spray. This requires an understanding of the pharmacological properties and delivery systems of opioids.

**Why the Correct Answer is Right**
The correct answer is a nasal spray formulation of naloxone, which is used for emergency treatment of opioid overdose. It works by rapidly reversing the effects of opioids at the opioid receptors in the brain, including mu, kappa, and delta receptors. Naloxone is a competitive antagonist at these receptors, meaning it binds to the receptor and prevents the opioid from binding and exerting its effects.

**Why Each Wrong Option is Incorrect**
**Option A:** Fentanyl is a potent opioid agonist that is commonly used in transdermal patches, lozenges, and injectable formulations, but not typically as a nasal spray.
**Option B:** Oxycodone is a Schedule II opioid agonist available in oral tablets, capsules, and liquid formulations, but not as a nasal spray.
**Option C:** Morphine is a Schedule II opioid agonist available in oral tablets, injectable formulations, and suppositories, but not as a nasal spray.

**Clinical Pearl / High-Yield Fact**
Naloxone nasal spray is a lifesaving medication for reversing opioid overdose, and it is essential to recognize its unique formulation and rapid onset of action.

**Correct Answer:** D. Naloxone