The d electron configuration of $Cr^{2+}, Mn^{2+}, Fe^{2+}$ and $Ni^{2+}$ are $3d^4$, $3d^5$, $3d^6$ and $3d^8$ respectively. Which one of the following aqua complex will exhibit the minimum paramagnetic behaviour ? <br>(At. No. Cr = 24, Mn= 25, Fe = 26, Ni = 28)
