Concept:Polymerization requires molecules with reactive multiple bonds, such as alkenes.Explanation:• C2H4 is ethene, an alkene with a carbon-carbon double bond.• Ethene undergoes addition polymerization to form polyethene:nCH2=CH2→(−CH2−CH2−)n• C2H5COOH, C2H6, and C2H5OH do not readily undergo addition polymerization because they lack C=C double bonds.Answer:A. C2H4