Which one of the following is a tridentate ligand

H2N¯−CH2−CH2−NH¯−CH2−CH2−NH2¯ is diethylene triamine, a tridentate ligand (dien). H2N-CH23-NH2 is trimethylenediaminetn a bidentate ligand.H2N¯−CH2−CH2−NH¯−CH2−CH2−NH¯-CH2-CH2-NH2¯  is triethelyne tetraamine, a tetradentate ligand (trien)EDTA is a hexadentate ligand.