(A) [Fe(C2O4)3]3− has oxalate ion as ligand which leads to chelation thus maximum stability among given complexes. (B) Stability : [Cu(NH3)4]2+<[Cu(en)2]2+; due to higher CFSE and chelation. (C) K4[Fe(CN)6]⇒Fe2+=[Ar]3d6 In presence of SFL the electronic configuration of Fe+2[t2g6,eg0], thus d2sp3 hybridized. (D) [Fe(NO2)3Cl3]3− has NO2− as ambidentate ligand thus can show linakge isomerism. (E) NO2− and SCN− both are ambidentate ligands.