Unleaded gasoline does not reduce carbon emissions. The lead was added to fuel ideally for vehicles to reduce the knocking of engines. Lead in its chemical structure also increased fuel octane levels. When lead was discovered to be a neurotoxin, it was banned as an additive in fuel in most countries.
Well here's an image of the things that do occur (different phases). You can see which ones are are right in the answer choices and pick out the wrong one. I hope this helps...
