Which of the following complexes will have the lowest value of $\Delta_0$?

The Crystal Field Stabilization Energy $(CFSE)$ and magnetic moment (spin-only) of an octahedral aqua complex of a metal ion $(M^{2+})$ are $-0.8\, \Delta_{0}$ and $3.87\, BM$,respectively. Identify $(M^{2+})$:

Match the $LIST$-$I$ with $LIST$-$II$:

List-$I$ (Electronic configuration of tetrahedral metal ion)	List-$II$ (Crystal Field Stabilization Energy $(\Delta_t)$)
$A$. $d^2$	$I$. $-0.6$
$B$. $d^4$	$II$. $-0.8$
$C$. $d^6$	$III$. $-1.2$
$D$. $d^8$	$IV$. $-0.4$

The crystal field stabilization energy $(CFSE)$ of $[Fe(H_2O)_6]Cl_2$ and $K_2[NiCl_4]$,respectively,are

The configurations of the complexes of manganese $A$ and $B$ respectively are $t_{2g}^3 e_g^1$ and $t_{2g}^4 e_g^0$. Then $A$ and $B$ are:

Assertion : Potassium ferrocyanide is diamagnetic,whereas potassium ferricyanide is paramagnetic.
Reason : Crystal field splitting in ferrocyanide ion is greater than that of ferricyanide ion.