Which of the following complexes can exist as enantiomers? Draw their structures

$\left(\mathrm{a}\right)$ $\mathrm{cis}-{\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_4{\mathrm{Br}}_2\right]}^{+}$

$\left(\mathrm{b}\right)$ $\mathrm{cis}-{\left[\mathrm{Cr}{\left({\mathrm{H}}_2\mathrm{O}\right)}_2(\mathrm{en}{)}_2\right]}^{3+}$

$\left(\mathrm{c}\right)$ $\left[\mathrm{Cr}(\mathrm{gly}{)}_3\right]$

$\left(\mathrm{d}\right)$ ${\left[\mathrm{Cr}(\mathrm{en}{)}_3\right]}^{3+}$

$\left(\mathrm{e}\right)$ $\mathrm{cis}-{\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_2(\mathrm{en}{)}_2\right]}^{2+}$

$\left(\mathrm{f}\right)$ $\mathrm{trans}-{\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_2(\mathrm{en}{)}_2\right]}^{2+}$

Draw the structures of the following metal carbonyls

$\left(\mathrm{a}\right)$ $\left[\mathrm{V}(\mathrm{CO}{)}_6\right]$

$\left(\mathrm{b}\right)$ $\left[Cr(\mathrm{CO}{)}_6\right]$

$\left(\mathrm{c}\right)$ $\left[{\mathrm{Mn}}_2(\mathrm{CO}{)}_{10}\right]$

$\left(\mathrm{d}\right)$ $\left[\mathrm{Fe}(\mathrm{CO}{)}_5\right]$

$\left(\mathrm{e}\right)$ $\left[\mathrm{Ni}(\mathrm{CO}{)}_4\right]$

The figure represents the synergic bonding interaction in metal carbonyl complex. On the basis of this explain the following:
$\left(\mathrm{i}\right)$ The strength of Metal-ligand bond.
$\left(\mathrm{ii}\right)$ The bond order of $\mathrm{CO}$ in carbonyl complex as compared to bond order in carbon monoxide.