**Core Concept**
The Minimum Alveolar Concentration (MAC) is a measure of anesthetic potency, with higher values indicating lower potency. It is defined as the alveolar concentration of an inhaled anesthetic that prevents movement in 50% of subjects in response to a painful stimulus.

**Why the Correct Answer is Right**
The anesthetic with the maximum MAC is essentially the one that requires the highest concentration to achieve the same effect as other anesthetics, meaning it is the least potent. Among common anesthetics, nitrous oxide has the highest MAC, reflecting its low potency.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because while it may have a high MAC, it is not the highest among the options provided.
**Option B:** Incorrect as it does not represent the anesthetic with the maximum MAC value.
**Option D:** Incorrect because, similar to options A and B, it does not have the highest MAC value among anesthetics.

**Clinical Pearl / High-Yield Fact**
Remembering that nitrous oxide has the highest MAC among anesthetics is crucial for understanding its potency and usage in clinical settings. Its high MAC value indicates lower potency, requiring higher concentrations for anesthesia.

**Correct Answer:** D. Nitrous oxide.