Benzene reacts with hydrogen in the presence of nickel catalyst at 180⁰C to give

Correct answer: cyclohexane.

Explanation: Benzene (C₆H₆) undergoes catalytic hydrogenation with H₂ over Ni at about 180 °C, adding three equivalents of hydrogen across the ring to give cyclohexane (C₆H₁₂): C₆H₆ + 3H₂ → C₆H₁₂.

• Xylene and toluene: methylated benzenes formed by alkylation, not by hydrogenation.
• Cyclopentane: wrong ring size; hydrogenation does not change the carbon skeleton.