**Core Concept**
The mechanism of action of sodium nitrite in cyanide poisoning involves the induction of methemoglobinemia, a condition where a significant amount of hemoglobin is converted to methemoglobin. This process is crucial because methemoglobin has a higher affinity for cyanide than cytochrome c oxidase.

**Why the Correct Answer is Right**
Sodium nitrite acts by releasing nitric oxide, which then converts hemoglobin to methemoglobin. Methemoglobin binds to cyanide, forming cyanomethemoglobin, thus reducing the amount of cyanide available to bind to cytochrome c oxidase in mitochondria. This mitigates the inhibition of cellular respiration caused by cyanide.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because it doesn't relate to the specific mechanism of sodium nitrite in treating cyanide poisoning.
**Option B:** Incorrect as it's not the primary mechanism through which sodium nitrite exerts its effect in cyanide poisoning.
**Option C:** Incorrect because, although related to the general management of cyanide poisoning, it doesn't specifically describe the action of sodium nitrite.

**Clinical Pearl / High-Yield Fact**
Remember, the treatment of cyanide poisoning often involves a combination of sodium nitrite and sodium thiosulfate. Sodium nitrite induces methemoglobinemia, while sodium thiosulfate acts as a substrate for the enzyme rhodanese, converting cyanide to thiocyanate, which is less toxic.

**Correct Answer:** D. Induction of Methemoglobinemia.