**Core Concept**
Nitrous oxide is a colorless gas used for its analgesic and anxiolytic properties in dental procedures. Its administration is a crucial aspect of dental anesthesia.

**Why the Correct Answer is Right**
Nitrous oxide works by inducing a state of relaxation and reducing anxiety through its action on the central nervous system. When inhaled, it rapidly crosses the blood-brain barrier, where it binds to GABA receptors, enhancing the inhibitory effects of GABA, a neurotransmitter that helps to calm neuronal activity. This results in a decrease in anxiety and pain perception. For this reason, nitrous oxide is typically administered through inhalation, allowing for rapid onset and precise control over the depth of sedation.

**Why Each Wrong Option is Incorrect**
**Option B:** Oral administration of nitrous oxide is not feasible due to its gas state and the difficulty in achieving a therapeutic concentration in the bloodstream through the gastrointestinal tract.

**Option C:** Intramuscular injection of nitrous oxide is not a viable option, as it would be difficult to administer and would not allow for the rapid onset of action required for effective analgesia and anxiolysis.

**Option D:** Intravenous administration of nitrous oxide is not commonly practiced due to its potential for causing respiratory depression and other systemic effects when administered in high concentrations.

**Clinical Pearl / High-Yield Fact**
Nitrous oxide is often used in combination with oxygen to prevent hypoxia and ensure a safe and effective anesthetic experience for patients.

**✓ Correct Answer: A. Inhalation. Nitrous oxide is administered through inhalation to induce relaxation and reduce anxiety in dental procedures.**