Question

The oxide which cannot act as a reducing agent is a- CO2 B- ClO2 C- NO2 D- SO2

Answer 1

Its CO2 because C in CO2 has an oxidation of +4.C can have a maximum of +4 thus CO2 cannot undergo oxidation thus it cannot act as a reducing agent.

Answer 2

The oxide which cannot act as reducing agent is a- $\mathrm{CO}_{2}$.

Explanation:

A reducing agent is the one that loses its electrons and gets oxidized in a chemical reaction. An oxide is a “binary compound of oxygen” with a metal or non-metal. Theoretically, when a metal or non-metal in any oxide is in its “highest possible oxidation state”, it cannot be oxidized and thus cannot act as a "reducing agent".

In $\mathrm{CO}_{2}$, carbon or C is in its “maximum oxidation state” of +4 and so, it cannot be further oxidized and cannot be a reducing agent.