Correct answer
Carbon dioxide (CO₂).
Carbon dioxide (CO₂), produced by burning carbon-containing fuels. Combustion engines may also emit other greenhouse gases, including methane and nitrous oxide, in smaller quantities. It is therefore incorrect to say they never emit methane. Battery-electric vehicles produce no tailpipe gases while driving, although emissions are associated with other lifecycle stages.
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Methane as the predominant gas in every case.
Pure oxygen as the principal greenhouse gas.
Carbon dioxide (CO₂).
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