which is composed of alkenes?\no welding torch fuel\no polystyrene cups\no propane gas\no degreaser…

Answer:

welding torch fuel

Explanation:

Step1: Identify alkene - related substances

Alkenes are hydrocarbons with carbon - carbon double bonds. Welding torch fuel often contains acetylene ($C_2H_2$), which is an alkyne, but also may contain other alkenes. Polystyrene is a polymer made from styrene (an aromatic hydrocarbon). Propane ($C_3H_8$) is an alkane. Hexane ($C_6H_{14}$) is an alkane. So the most likely option composed of alkenes is welding torch fuel.