Which of the gases listed is the poisonous gas most likely to be found in a closed compartment involved in a fire?

Correct Answer: Option D — Carbon monoxide

Carbon monoxide is a byproduct of incomplete combustion, frequently generated during shipboard fires in enclosed spaces. It is highly toxic because it binds to hemoglobin more effectively than oxygen, leading to rapid asphyxiation. Its presence is a primary danger to firefighting teams and personnel investigating smoke-filled compartments.