**Core Concept**
The electron transport chain (ETC) is a critical process in cellular respiration where electrons are passed through a series of protein complexes, generating ATP. Cyanide is a potent inhibitor that disrupts this process, leading to cellular asphyxiation.

**Why the Correct Answer is Right**
Cyanide binds to the iron-sulfur centers in Complex IV (cytochrome c oxidase) of the electron transport chain, preventing the transfer of electrons and the subsequent pumping of protons across the mitochondrial inner membrane. This inhibition halts the production of ATP and leads to cellular hypoxia. The unique binding affinity of cyanide to the iron-sulfur centers makes Complex IV the primary target of cyanide toxicity.

**Why Each Wrong Option is Incorrect**
**Option A:** NADH dehydrogenase (Complex I) is not the primary target of cyanide. While it's true that cyanide can affect Complex I indirectly, its primary binding site is in Complex IV.
**Option B:** Succinate dehydrogenase (Complex II) is not directly affected by cyanide, as it operates in the mitochondrial matrix and doesn't have the same iron-sulfur centers as Complex IV.
**Option C:** Cytochrome b-c1 complex (Complex III) is also not the primary target of cyanide, although it can be indirectly affected by the disruption of electron flow from Complex IV.

**Clinical Pearl / High-Yield Fact**
Cyanide toxicity is a classic example of a "high-hill" poison, where a small dose can be lethal due to its potent inhibition of cellular respiration. Clinicians should be aware of the signs and symptoms of cyanide poisoning, including headache, dizziness, and respiratory failure, to provide prompt treatment with antidotes like hydroxocobalamin.

**Correct Answer:** C. Cytochrome c oxidase (Complex IV) is the primary target of cyanide in the electron transport chain.