The correct answer is $\boxed{\text{B}}$, ethene.
Ethene is an odd compound because it has an odd number of carbon atoms.
The other options, propane, methane, and ethane, all have an even number of carbon atoms.Ethene is a hydrocarbon with the chemical formula $\ce{C2H4}$. It is a colorless, flammable gas that is used in the production of plastics, rubber, and other chemicals. Ethene is also the simplest alkene, which is a type of hydrocarbon that contains one or more double bonds between carbon atoms.
Propane is a hydrocarbon with the chemical formula $\ce{C3H8}$. It is a colorless, flammable gas that is used as a fuel in heating and cooking appliances. Propane is also used as a refrigerant and in the production of plastics and other chemicals.
Methane is a hydrocarbon with the chemical formula $\ce{CH4}$. It is a colorless, odorless, and flammable gas that is the main component of natural gas. Methane is also used as a fuel in heating and cooking appliances.
Ethane is a hydrocarbon with the chemical formula $\ce{C2H6}$. It is a colorless, odorless, and flammable gas that is used as a fuel in heating and cooking appliances. Ethane is also used as a refrigerant and in the production of plastics and other chemicals.