$[Co(NH_3)_5SO_4]Br$ and $[Co(NH_3)_5Br]SO_4$ are a pair of isomers.

How many geometrical isomers are possible in the following coordination entities?
$(i)$ $[Cr(C_2O_4)_3]^{3-}$
$(ii)$ $[Co(NH_3)_3Cl_3]$

Which of the following will have two stereoisomeric forms?
$I. [Cr(NO_3)_3(NH_3)_3]$
$II. K_3[Fe(C_2O_4)_3]$
$III. [CoCl_2(en)_2]^+$
$IV. [CoBrCl(ox)_2]^{3-}$

Which of the following complexes exhibit geometrical isomerism?
$I$) $[Co(en)(NH_3)_2 Cl_2] Cl$
$II$) $[Co(NH_3)_4 Cl_2] Cl$
$III$) $[Co(en)_3] Cl_3$
$IV$) $[Co(en)_2 Cl_2] Br$

Which of the following complexes exhibits optical activity?

There are four complexes of $Ni$. Select the complex(es) which will be attracted by a magnetic field:
$(I) \ [Ni(CN)_4]^{2-}, \ (II) \ [NiCl_4]^{2-}, \ (III) \ [Ni(CO)_4]$
$(IV) \ [Ni(H_2O)_6]^{2+}$