Which of the following ligands has the highest field strength?

Which of the following ligands causes the maximum splitting of $d$-orbitals?

Which of the following correctly represents the order of ligands in the spectrochemical series?

The $3d$ metal ions form coloured compounds because the energy corresponding to the following lies in the visible range of the electromagnetic spectrum:

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).

What is the correct order of increasing field strength for the ligands $NH_3$,$en$,$CN^-$,and $CO$?