The correct answer is Carbon Monoxide (CO). When organic matter is burned with insufficient oxygen, it leads to incomplete combustion and the production of various gases, including carbon monoxide. Carbon monoxide is a colorless, odorless gas that is extremely poisonous and can be fatal in high concentrations.Carbon dioxide (CO2) is a product of complete combustion and is not produced when there is insufficient oxygen.Benzene is a hydrocarbon compound composed of six carbon atoms and six hydrogen atoms, and it is not produced from combustion.Methane (CH4) is a hydrocarbon compound composed of one carbon atom and four hydrogen atoms, and it is not produced from combustion.Mercury is a metallic element and is not related to combustion.