Which of the following pair of ions can not be separated by ${\mathrm{H}}_2\mathrm{S}$  and dil. HCl 

${\mathrm{Bi}}^{+3} \mathrm{and} {\mathrm{Sn}}^{+4}$both will form ppt with $$\begin{gathered} {\mathrm{H}}_{2}S ; \\ {\mathrm{Bi}}^{+3}+{\mathrm{S}}^{2-}\to {\mathrm{Bi}}_2{\mathrm{S}}_3(\mathrm{Orange} \mathrm{PPt}) \end{gathered}$$
${\mathrm{Sn}}^{+4}+{\mathrm{S}}^{2-}\to {\mathrm{SnS}}_2$(Dirty yellow PPt)
${\mathrm{Al}}^{+3},{\mathrm{Zn}}^{+2} \mathrm{and} {\mathrm{Ni}}^{+2}$will not form ppt with H₂S in acidic medium