Which of the following gases are classified as narcotic gases?

Narcotic gases are substances that can induce a state of narcosis, leading to symptoms such as dizziness, disorientation, and unconsciousness due to their effects on the central nervous system. The correct choice lists carbon monoxide (CO), carbon dioxide (CO2), hydrogen cyanide (HCN), and oxygen (O) as examples of these narcotic gases.

Carbon monoxide is particularly dangerous because it binds to hemoglobin in the blood more effectively than oxygen, reducing the amount of oxygen transported in the bloodstream and leading to symptoms of hypoxia. Hydrogen cyanide, derived from burning materials like plastics and other carbon-containing substances, is a highly toxic gas that can inhibit cellular respiration. Carbon dioxide can act as a narcotic in high concentrations, contributing to asphyxiation and leading to unconsciousness.

In contrast, the other options do not contain gases that are recognized for their narcotic properties. While gases like those found in the other choices may still pose serious health risks, they are not classified as narcotic gases. For instance, gases like sulfur dioxide and nitrogen dioxide are primarily irritants rather than narcotics, while the hydrocarbons listed are fuels and may not exhibit narcotic effects until in extremely high concentrations.