The correct option is A CO2+H2O
The Complete Combustion of Natural Gas - Methane.
Complete combustion happens when the hydrocarbon burns in an excess of air. An excess of air means that there is more than enough oxygen to cause all of the carbon to turn into carbon dioxide.The methane gas burns with a clear blue flame.
CH4+2O2⟶CO2+2H2O
The reaction is exothermic (it gives out heat). The heat released from burning natural gas is used for central heating and to generate electricity.