The $d$ -electron configurations of ${\text{Cr}}^{2+}$, ${\text{Mn}}^{2+}$, ${\text{Fe}}^{2+}$ and ${\text{Ni}}^{2+}$ are $3d^4$, $3d^5$, $3d^6$ and $3d^8$ respectively. Which one of the following aqua complexes will exhibit the minimum paramagnetic behaviour?

1. A
   $[\text{Mn}({\text{H}}_2\text{O}{)}_6{]}^{2+}$
2. B
   $[\text{Fe}({\text{H}}_2\text{O}{)}_6{]}^{2+}$
3. C
   $[\text{Ni}({\text{H}}_2\text{O}{)}_6{]}^{2+}$
4. D
   $[\text{Cr}({\text{H}}_2\text{O}{)}_6{]}^{2+}$