Find the number of complexes following sidgwick EAN rule:

${\left[\mathrm{Ag}(\mathrm{CN}{)}_2\right]}^{-}$            ${\left[{\mathrm{Hg}}_4\right]}^{2-}$

${\left[\mathrm{Ti}(\mathrm{CO}{)}_6\right]}^{2-}$,                 $\left[\mathrm{Ti}{\left(\sigma -{\mathrm{C}}_5{\mathrm{H}}_5\right)}_2{\left(\pi -{\mathrm{C}}_5{\mathrm{H}}_5\right)}_2{]}^{\circ }\right.$

$\left[\mathrm{Fe}(\mathrm{CN}{)}_6{\mathrm{NO}}^{2-}\right.$

When the total number of electrons in the metal ion reaches the atomic number of the noble gas in that series, the metal ion in a coordination complex will stop absorbing electrons.

$\begin{array}{l}{\left[\mathrm{Ag}(\mathrm{CN}{)}_2\right]}^{-}\Rightarrow 47-1+4=50\\ {\left[{\mathrm{HgI}}_4\right]}^{2-}\Rightarrow 80-2+8=86\\ {\left[\mathrm{Ti}(\mathrm{CO}{)}_6\right]}^{2-}\Rightarrow 22+2+12=36\\ \left[\mathrm{Ti}{\left(\sigma -{\mathrm{C}}_5{\mathrm{H}}_5\right)}_2{\left(\pi -{\mathrm{C}}_5{\mathrm{H}}_5\right)}_2\right]\Rightarrow 22-4+4+12=34\\ \left[\mathrm{Fe}\left({\mathrm{CN}}_6{\mathrm{NO}}^{2-}\Rightarrow 26-3+12=35\right.\right.\end{array}$

Here, complexes which follow sidgwick EAN rule are:

${\left[{\mathrm{Hg}}_4\right]}^{2-}$, ${\left[\mathrm{Ti}(\mathrm{CO}{)}_6\right]}^{2-}$

Hence correct answer is 0002.