In the formation of $K_4[Fe(CN)_6]$,the hybridisation involved is

Which complex compound possesses $sp^3d^2$ hybridisation?

In the crystal of $CuSO_4 \cdot 5H_2O$,the copper atom is coordinated by:

For octahedral $Mn(II)$ and tetrahedral $Ni(II)$ complexes,consider the following statements:
$(I)$ Both the complexes can be high spin.
$(II)$ $Ni(II)$ complex can very rarely be low spin.
$(III)$ With strong field ligands,$Mn(II)$ complexes can be low spin.
$(IV)$ Aqueous solution of $Mn(II)$ ions is yellow in color.

Number of identical $Cr-O$ bonds in dichromate ion $Cr_2O_7^{2-}$ is

Identify the correctly matched set from the following: