Evaluating properties and reactions of unsaturated hydrocarbon X

Steps:

• Statement 1 is true: All hydrocarbons, including X, undergo complete combustion in air to produce CO₂ and H₂O.
• Statement 2 is false: Unsaturated compounds like X decolorize bromine water (brown to colorless), not the reverse.
• Statement 3 is false: The structure of X differs from propene (CH₃CH=CH₂), as shown.
• Statement 4 is true: Hydrogenation of X's C=C bond converts it to a C-C single bond, increasing the total number of C-C single bonds.

Why B is correct:

• B pairs statements 1 and 4, both accurate for X as an alkene: combustion follows the general formula CₙHₘ + O₂ → CO₂ + H₂O, and hydrogenation (C=C + H₂ → C-C) adds single bonds per the reaction mechanism.

Why the others are wrong:

• A includes false statement 2, misstating bromine test.
• C includes false statement 2 and incorrect identification of X as propene.
• D includes false statement 3, as X's structure is not propene.

Final answer: B