In 2MnO₄− + 5C₂O₄²− + 16H+ → 2Mn²⁺ + 10CO₂ + 8H₂O, which species contains the element oxidized?
C (+3 in C₂O₄²−) to +4 in CO₂ is oxidized; Mn (+7 to +2) is reduced.
Ref: NCERT Class 11 Chemistry > Chapter 7: Redox Reactions > Topic: Electrode Potential and Electrochemical Series and Galvanic Cells