$\left[\mathrm{Ni}^{\mathrm{II}} \mathrm{L}_{6}\right]^{\mathrm{n}+\text { or } \mathrm{n}-}$ shows absorption bands at 8500,15400 , and $26000 \mathrm{cm}^{-1}$ whereas $\left[\mathrm{Ni}^{\mathrm{II}} \mathrm{L}^{\prime}{ }_{6}\right]^{\mathrm{n}+\text { or } \mathrm{n}-}$ at 10750,17500 and $28200 \mathrm{cm}^{-1} . \mathrm{L}$ and $\mathrm{L}^{\prime}$ are respectively
(a)$\mathrm{OH}^{-1}$ and $\mathrm{N}_{3}^{-}$
(b)$\mathrm{Cl}^{-1}$ and $\mathrm{I}^{-}$
(c)$\mathrm{NCS}^{-1}$ and $\mathrm{RCO}_{2}^{-}$
(d)$\mathrm{H}_{2} \mathrm{O}$ and $\mathrm{NH}_{3}$