In organic quantitative analysis, CuO acts as

The elements [H, C, and S] contained in the organic complex are oxidized by the oxidising agent CuO to produce their corresponding oxides.

Quantitative analysis is a way of determining the amount of elements or molecules created during a chemical reaction. Organic compounds are made up of carbon, hydrogen, oxygen, nitrogen, phosphorus, sulphur, and halogens.

Hence, the correct option is: (B) Oxidizing agent