${\mathrm{H}}_2\mathrm{S}$ will precipitate the sulphide of all the metals from the solution of chlorides of Cu, Zn and Cd if:

If the solution of Cu, Zn, and Cd chlorides is aqueous, ${\mathrm{H}}_2\mathrm{S}$ will precipitate the sulphides of all the metals from the solution. Cu, Cd, Zn, and Mn may all form sulphide precipitates when ${\mathrm{H}}_2\mathrm{S}$ is present in a neutral solution.

The solution is aqueous and solution is alkaline because when ${\mathrm{Na}}_2{\mathrm{CO}}_3$ dissolves in water, hydrolysis occurs, resulting in the formation of strong base (NaOH) and weak acid $\left({\mathrm{H}}_2{\mathrm{CO}}_3\right)$. As a result, the nature of its aqueous solution is alkaline.

Hence correct options are a and d.