Task: Question Answering
Input (English): 3 Cl−(aq) + 4 CrO_4^2−(aq) + 23 H+(aq) → 3 HClO2(aq) + 4 Cr3+(aq) + 10 H2O(l). In the reaction shown above, Cl−(aq) behaves as
(A)an acid (B)a base (C)a catalyst (D)a reducing agent
Output (English): D