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

Three complexes,$[CoCl(NH_3)_5]^{2+} (I)$,$[Co(NH_3)_5H_2O]^{3+} (II)$ and $[Co(NH_3)_6]^{3+} (III)$ absorb light in the visible region. The correct order of the wavelength of light absorbed by them is

Among the following species,the one which causes the highest $CFSE, \Delta _0$ as a ligand is

In which case is a $d^7$ complex species more stable?

Identify the correct decreasing order of wavelength of light absorbed for the following complex ions:
$I. [Co(H_2O)_6]^{3+}$
$II. [Co(CN)_6]^{3-}$
$III. [CoI_6]^{3-}$
$IV. [Co(en)_3]^{3+}$

Given below are two statements,one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: $[CoCl(NH_3)_5]^{2+}$ absorbs at a lower wavelength of light with respect to $[Co(NH_3)_5(H_2O)]^{3+}$.
Reason $R$: It is because the wavelength of the light absorbed depends on the oxidation state of the metal ion.
In the light of the above statements,choose the correct answer from the options given below: