In Coordination Chemistry, the Coordination Complex is formed when the ligands make coordinate covalent bond with the central Metal atom. The ligand may be Monodentate or Polydentate. Monodentate ligands form only one bond with the central Metal, while polydentate forms two or more bonds with the central metal atom. In given options, EDTA is a Hexadentate ligand, Oxalate is a Bidentate ligand, while Nitrite and Carbon monoxide are monodentate ligands. Sites involved on bond formation of each ligand with metal are highlighted red (Figure).
