Which one of the following was used as a chemical weapon in the first world war ?
A
Carbon monoxide
B
Hydrogen cyanide
C
Mustard gas
D
Water gas
Correct Answer: Mustard gas
Although the Germans were the first to use phosgene on the battlefield, it became the primary chemical weapon of the Allies. Phosgene was responsible for 85% of chemical-weapons fatalities during World War I. Mustard gas, a potent blistering agent, was dubbed King of the Battle Gases.