Final answer:
In the reaction 4HCl + MnO₂ → Cl₂ + 2H₂O + MnCl₂, MnO₂ acts as the oxidizing agent by accepting electrons and being reduced from an oxidation state of +4 to +2.
Step-by-step explanation:
The question pertains to identifying the oxidizing agent in a redox reaction involving hydrochloric acid (HCl) and manganese dioxide (MnO₂), which produces chlorine gas (Cl₂), water (H₂O), and manganese(II) chloride (MnCl₂).
In this reaction, MnO₂ serves as the oxidizing agent because it accepts electrons from HCl, which is being oxidized. During the reaction, MnO₂ is reduced as its oxidation state decreases from +4 in MnO₂ to +2 in MnCl₂. The reducing agent, HCl, loses electrons and becomes oxidized in the process, producing Cl₂. Hence, the correct answer is (c) MnO₂.