Reduction in redox reactions involves gain of electrons

Steps:

• Identify oxidation states: In TiO2, Ti is +4 and O is -2; Cl2 is 0.
• In products, TiCl4 has Ti +4 and Cl -1; O2 has O 0.
• Compare changes: Cl decreases from 0 to -1 (gains electrons, reduced); O increases from -2 to 0 (oxidized); Ti unchanged.
• Confirm: Chlorine is reduced as it accepts electrons from oxygen.

Why B is correct:

• Chlorine is reduced because its oxidation state decreases from 0 in Cl2 to -1 in TiCl4, per the definition of reduction as electron gain.

Why the others are wrong:

• A: Carbon is not present in the reaction.
• C: Oxygen is oxidized, as its oxidation state increases from -2 to 0.
• D: Titanium's oxidation state remains +4 in both reactant and product.

Final answer: B