**Core Concept**
Cyanide poisoning occurs due to the inhibition of cellular respiration, specifically at the level of cytochrome c oxidase in the mitochondria. This disruption results in a decrease in the production of adenosine triphosphate (ATP), leading to cellular asphyxiation.

**Why the Correct Answer is Right**
Cyanide binds to the iron atom within cytochrome c oxidase, preventing the transfer of electrons and thus halting oxidative phosphorylation. This leads to an accumulation of oxygen within the cell, but due to the lack of ATP production, cellular energy levels are severely depleted. The resulting cellular asphyxiation is responsible for the rapid progression of cyanide poisoning.

**Why Each Wrong Option is Incorrect**
**Option A:** Cyanide is not primarily an inhibitor of the electron transport chain in the mitochondria; rather, it specifically targets cytochrome c oxidase.
**Option B:** Methemoglobinemia, a condition caused by the accumulation of methemoglobin, is a consequence of nitrate or nitrite poisoning, not cyanide poisoning.
**Option C:** While cyanide does have a rapid onset, it is not primarily due to its rapid absorption; rather, it is due to its immediate inhibition of cytochrome c oxidase.

**Clinical Pearl / High-Yield Fact**
Cyanide poisoning is often associated with smoke inhalation, particularly from fires involving plastics or other synthetic materials. This is because these materials release cyanide gas when burned.

**Correct Answer:** C. Inhibition of cytochrome c oxidase.