Final answer:
Oil releases more than twice as much CO₂ compared to natural gas.
Step-by-step explanation:
When compared to natural gas, oil releases more than twice as much CO₂.
While all forms of fossil fuels produce a ratio of approximately 3 units of CO₂ for every unit of fuel, coal has a lower energy density and a slightly higher CO₂-to-fuel mass ratio, making it more carbon-intense than natural gas.