Correct Option
Mustard gas, chemically known as sulphur mustard (C₄H₈Cl₂S), was a prominent chemical warfare agent extensively deployed during World War I. Introduced by Germany in 1917, it is classified as a vesicant due to its ability to cause severe blistering of the skin, eyes, and respiratory tract.
Its effects included painful burns, eye irritation often leading to temporary blindness, and significant damage to the lungs upon inhalation. Although not always immediately lethal, its debilitating nature and profound psychological impact made it a highly effective weapon of attrition.
Incorrect Options
Carbon monoxide (a) is a highly toxic gas but was not utilized as a chemical weapon during World War I.
Hydrogen cyanide (b) is a lethal chemical, but its primary use as a chemical warfare agent, particularly in gas chambers, was observed in later conflicts like World War II, not World War I.
Water gas (d) is an industrial fuel, a mixture primarily composed of carbon monoxide and hydrogen, and was not employed as a chemical weapon.