Which substance blocks aerobic metabolism by interfering with the cell's use of oxygen?

Cyanide effectively blocks aerobic metabolism by interfering with the cell's ability to use oxygen. It does this by inhibiting the enzyme cytochrome c oxidase, which is crucial for the electron transport chain in aerobic respiration. When cyanide binds to this enzyme, it prevents cells from utilizing oxygen for energy production, leading to cellular asphyxiation despite the presence of oxygen in the blood.

In contrast, other substances listed have different mechanisms of action. Carbon monoxide, while it also affects oxygen transport, primarily binds to hemoglobin, reducing the blood's oxygen-carrying capacity, but does not directly block cellular oxygen utilization. Chlorine is a strong oxidizing agent and can cause damage to respiratory tissues, but does not specifically target mechanisms of aerobic metabolism. Formaldehyde is a chemical that can interfere with cellular function and protein structure but does not block oxygen utilization in the same way that cyanide does.