Compounds with spin-only magnetic moment equivalent to five unpaired electrons are

Among the given species $\mathrm{H}_{2} \mathrm{O}$ and $\mathrm{F}$ are weak field ligands and do not cause pairing of electrons in the central metal atom. As CN is a strong field ligand, it causes pairing of electrons in the central metal atom. Now, Oxidation state of : (b) Fe in $\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right] \mathrm{Cl}_{3}=(+) 3$ and electronic configuration of $\mathrm{Fe}^{3 +}$ ions is $\mathrm{3d}^{5} 4 \mathrm{s}^{0}$ i.e. have 5 unpaired electrons (c) Fe in $\mathrm{K}_{3}\left[\mathrm{FeF}_{6}\right]$ Oxidation no. of $\mathrm{Fe}=(+) 3$ electronic configuration of $\mathrm{Fe}^{3}$ is $\mathrm{3d}^{4} 4 \mathrm{s}^{0}$ i.e. have 5 unpaired electrons. (d) Oxidation state of $\mathrm{Mn}$ in $\mathrm{K}_{4}\left[\mathrm{MnF}_{6}\right]=(+) 2$ and electronic configuration of $\mathrm{Mn}^{2}+$ is $\mathrm{3d}^{5} 4 \mathrm{s}^{0}$ i.e., have 5 unpaired electrons. Hence, options (b) (c) and (d) are the correct options.