Which ligand among the following has the highest splitting power of $d$-orbitals of the central metal ion?

Given below are two statements: Statement $I$: Each electron in $e_g$ orbitals destabilizes the orbitals by $+0.6\Delta_o$ and each electron in the $t_{2g}$ orbitals stabilizes the orbitals by $-0.4\Delta_o$ in an octahedral field on the basis of crystal field theory. Statement $II$: All the $d$-orbitals of the transition metals have the same energy in their free atomic state but when a complex is formed the ligands destroy the degeneracy of these orbitals on the basis of crystal field theory. In the light of the above statements, choose the correct answer from the options given below:

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

Match List-$I$ with List-$II$.

List-$I$ (Coordination entity)	List-$II$ (Wavelength of light absorbed in $nm$)
$A$. $[CoCl(NH_3)_5]^{2+}$	$I$. $310$
$B$. $[Co(NH_3)_6]^{3+}$	$II$. $475$
$C$. $[Co(CN)_6]^{3-}$	$III$. $535$
$D$. $[Cu(H_2O)_4]^{2+}$	$IV$. $600$

Choose the correct answer from the options given below:

Which of the following spectrochemical series is correct?

$A$ strong field ligand gives a complex which is generally called: