Concept:Unsaturated compounds containing a
C=C double bond readily undergo addition reactions.
Explanation:Addition reactions are typical of alkenes because their double bond can open to add new atoms or groups.
Butene is an alkene with a
C=C double bond, so it readily undergoes addition.
Ethane is an alkane with only single bonds, so it prefers substitution rather than addition.
Ethanol is an alcohol containing an
−OH group and does not readily undergo addition.
Benzene has a delocalised aromatic ring and usually undergoes substitution instead of addition.
Hence, among the given compounds, butene is the one that readily undergoes an addition reaction.
Answer:B. butene