**Core Concept**
McEwan Sign is a clinical finding associated with a specific type of poisoning. It is characterized by the presence of a peculiar odor in the breath or on the skin, which is a result of the metabolic byproducts of the toxin.

**Why the Correct Answer is Right**
The correct answer is related to a type of poisoning that involves the metabolism of a specific compound. The McEwan Sign is a classic finding in cases of cyanide poisoning. When cyanide is ingested, it is rapidly metabolized to thiocyanate, which is excreted in the urine and also present in the breath and skin, giving off a characteristic odor. This is due to the enzyme rhodanese, which catalyzes the conversion of cyanide to thiocyanate.

**Why Each Wrong Option is Incorrect**
* **Option A:** This is incorrect as McEwan Sign is not associated with arsenic poisoning, which has a different set of clinical manifestations, including gastrointestinal symptoms and skin lesions.
* **Option B:** This is incorrect as McEwan Sign is not seen in organophosphate poisoning, which presents with cholinergic symptoms such as muscle cramps, diarrhea, and excessive salivation.
* **Option C:** This is incorrect as McEwan Sign is not associated with cocaine poisoning, which has a different set of clinical manifestations, including euphoria, agitation, and cardiovascular effects.

**Clinical Pearl / High-Yield Fact**
McEwan Sign is a classic finding in cyanide poisoning and should be kept in mind when evaluating patients with suspected cyanide toxicity. The presence of this sign can help guide treatment and diagnosis.

**Correct Answer:** Not provided, however typically McEwan Sign is seen in **C. Cyanide poisoning**.