Cyanide is a poison that works by preventing oxygen from receiving electrons. Therefore, cyanide directly affects which stage of cellular respiration?

Cyanide's affect the electron transport chain of cellular respiration.

Explanation:

Cyanide's bind to ferric iron of cytochrome oxidase in the Mitochondria, inhibiting it and disrupt cellular respiration by affecting reduction of water to oxygen. This prevent cytochrome oxidase from performing it function which is to send electrons to oxygen in the electron transport chain during aerobic cellular respiration.

the answer would be..

b. sucking