**Core Concept**
Sodium nitrate is used as an antidote in cyanide poisoning, and its mechanism involves the conversion of cyanide to thiocyanate, which is less toxic.

**Why the Correct Answer is Right**
The mechanism of action of sodium nitrate in cyanide poisoning is through the formation of methemoglobin, an oxidized form of hemoglobin. Methemoglobin has a higher affinity for cyanide than cytochrome c oxidase, effectively binding and detoxifying cyanide. This process is facilitated by the presence of nitric oxide, which is formed from the breakdown of sodium nitrate. The resulting methemoglobin-cyanide complex is then excreted by the kidneys, thereby reducing the toxic effects of cyanide on cellular respiration.

**Why Each Wrong Option is Incorrect**
**Option A:** This is not a relevant mechanism of action for sodium nitrate in cyanide poisoning. Sodium nitrate does not stimulate the production of nitric oxide in this context.
**Option B:** While sodium nitrate can increase nitric oxide levels, this is not the primary mechanism by which it counteracts cyanide poisoning.
**Option C:** This option is incorrect because sodium nitrate does not directly inhibit cytochrome c oxidase, the enzyme targeted by cyanide.

**Clinical Pearl / High-Yield Fact**
In cyanide poisoning, the antidote sodium nitrite (not sodium nitrate) is typically administered first to induce methemoglobinemia, followed by sodium thiosulfate to facilitate the conversion of cyanide to thiocyanate.

**Correct Answer:** C.