In an octahedral complex $[Mabcdef]$,the total number of theoretical isomers is:

Which of the following exhibits optical isomerism?

What is the magnetic moment of a divalent ion in aqueous solution if its atomic number is $28$ (in $BM$)?

Amongst $FeCl_{3} \cdot 3H_{2}O$,$K_{3}[Fe(CN)_{6}]$ and $[Co(NH_{3})_{6}]Cl_{3}$,the spin-only magnetic moment value of the inner-orbital complex that absorbs light at the shortest wavelength is $B.M.$ [nearest integer].

Draw the structures of optical isomers of:
$(i)$ $[Cr(C_2O_4)_3]^{3-}$
$(ii)$ $[PtCl_2(en)_2]^{2+}$
$(iii)$ $[Cr(NH_3)_2Cl_2(en)]^{+}$

Which among the following metal complexes exhibits optical activity? ($AA$ = bidentate ligand; $A, X$ = monodentate ligands)