The set which does not have ambidentate ligand(s) is :

<b>Option A :</b> <br/><br/>- $\mathrm{C}_{2} \mathrm{O}_{4}{ }^{2-}$ (Oxalate) is a bidentate ligand. It always binds through its two oxygen atoms. <br/><br/>- $\mathrm{NO}_{2}{ }^{-}$ (Nitrite) is an ambidentate ligand. It can coordinate either through nitrogen or oxygen. <br/><br/>- $\mathrm{NCS}^{-}$ (Thiocyanate) can also bind through either nitrogen or sulfur, making it an ambidentate ligand. <br/><br/><b>Option B :</b> <br/><br/>- $\mathrm{C}_{2} \mathrm{O}_{4}{ }^{2-}$ (Oxalate) as mentioned earlier, is a bidentate ligand. <br/><br/>- Ethylene diamine (en) is also a bidentate ligand, as it always binds through its two nitrogen atoms. <br/><br/>- $\mathrm{H}_{2} \mathrm{O}$ (Water) is a monodentate ligand, binding only through one oxygen atom. <br/><br/><b>Option C :</b> <br/><br/>- $\mathrm{NO}_{2}^{-}$ as mentioned, is an ambidentate ligand. <br/><br/>- $\mathrm{C}_{2} \mathrm{O}_{4}{ }^{2-}$ as mentioned, is a bidentate ligand. <br/><br/>- $\mathrm{EDTA}^{4-}$ is a hexadentate ligand. It always binds through six donor atoms and is not ambidentate. <br/><br/><b>Option D :</b> <br/><br/>- $\mathrm{EDTA}^{4-}$ as mentioned, is a hexadentate ligand. <br/><br/>- $\mathrm{NCS}^{-}$ as mentioned, is an ambidentate ligand. <br/><br/>- $\mathrm{C}_{2} \mathrm{O}_{4}{ }^{2-}$ as mentioned, is a bidentate ligand. <br/><br/>From the above analysis, it's clear that Option B is the one that does not contain any ambidentate ligands. So, the correct answer is Option B.