Which one of the following is a strong field ligand?

On the basis of crystal field theory,explain why $Co(III)$ forms a paramagnetic octahedral complex with weak field ligands,whereas it forms a diamagnetic octahedral complex with strong field ligands.

Simplified absorption spectra of three complexes $(i), (ii)$ and $(iii)$ of $M^{n+}$ ion are provided below; their $\lambda_{max}$ values are marked as $A, B$ and $C$ respectively. The correct match between the complexes and their $\lambda_{max}$ values is
$(i)$ $[M(NCS)_6]^{(-6+n)}$
$(ii)$ $[MF_6]^{(-6+n)}$
$(iii)$ $[M(NH_3)_6]^{n+}$

Identify the weak field ligand from the following.

The complex that has the highest crystal field splitting energy $(\Delta)$ is

Write down the number of $3d$ electrons in each of the following ions:
$Ti^{2+}, V^{2+}, Cr^{3+}, Mn^{2+}, Fe^{2+}, Fe^{3+}, Co^{2+}, Ni^{2+}$ and $Cu^{2+}$
Indicate how you would expect the five $3d$ orbitals to be occupied for these hydrated ions (octahedral).