Explanation:

Any hydrocarbon fuel when oxidized in low presence of oxygen, it forms carbon monoxide instead of dioxide. So, statements 1 and 3 are correct.
Statement 2: Carbon dioxide (not carbon monoxide) is found naturally in groundwater, ice caps, glaciers etc.
Statement 4: The principal components of volcanic gases are water vapour (H2O), CO2, CO, SO2 or hydrogen sulphide, nitrogen, argon, helium, neon, methane and hydrogen.
Learning: It is also generated from natural and man-made fires (such as forest and bushfires, burning of crop residues, and sugarcane fire-cleaning). Carbon monoxide occurs dissolved in molten volcanic rock at high pressures in the Earth's mantle.
Worldwide, the largest source of carbon monoxide is natural in origin, due to photochemical reactions in the troposphere.