Which is a wrong combination?

Answer: Option D

Here, N₂-Amino acid, Fe-Cytochrome, and Mg-Chlorophyll are the correct combinations, whereas, Na-Protein is the wrong combination.
Sodium is not essential for the synthesis of protein. Nitrogen is one of the main body components, required for protein synthesis and production of several nitrogenous compounds such as hormones, neurotransmitters, and components of antioxidant defense.
Protein combining or protein complementing is a dietary theory for protein nutrition that purports to optimize the biological value of protein intake.