**Core Concept**
The coronary steal phenomenon occurs when there is a diversion of blood flow from a stenotic coronary artery to a non-stenotic area, reducing blood flow to the ischemic myocardium. This is often seen in patients with significant coronary artery disease.

**Why the Correct Answer is Right**
Nitrous oxide (N2O) can cause coronary steal phenomenon by dilating non-stenotic coronary arteries, thereby diverting blood flow away from the stenotic area. This is due to the vasodilatory effect of N2O on the smooth muscle of the coronary arteries. The mechanism is thought to be mediated by the release of endothelium-derived relaxing factor (EDRF), which is now known to be nitric oxide (NO).

**Why Each Wrong Option is Incorrect**
**Option A:** Sevoflurane is a commonly used inhalational anesthetic agent, but it is not typically associated with the coronary steal phenomenon. While it may have some vasodilatory effects, it is not as potent as N2O in causing this phenomenon.
**Option B:** Desflurane is a rapidly acting inhalational anesthetic agent, but it is not known to cause coronary steal phenomenon. In fact, it may even cause coronary vasoconstriction at high concentrations.
**Option C:** Isoflurane is another commonly used inhalational anesthetic agent, but it is not typically associated with the coronary steal phenomenon. While it may have some vasodilatory effects, it is not as potent as N2O in causing this phenomenon.

**Clinical Pearl / High-Yield Fact**
It is essential to be aware of the potential for coronary steal phenomenon when using N2O, particularly in patients with significant coronary artery disease. This can be mitigated by using a lower concentration of N2O or by using a different inhalational agent.

**Correct Answer:** C. Nitrous oxide.