Question

which is composed of alkenes?
welding torch fuel
polystyrene cups
propane gas
degreaser containing hexane

Explanation:

Alkenes are unsaturated hydrocarbons with a carbon - carbon double bond. Welding torch fuel often contains acetylene (an alkyne), polystyrene is made from styrene monomers (an aromatic hydrocarbon derivative), propane is an alkane, and hexane is also an alkane. None of the other options are composed of alkenes.

Answer:

None of the above options are correct as they do not contain alkenes.