In the analysis of basic radicals,the group reagent $H_2S$ gas is generally used in which groups?

Among the following cations,the number of cations which will give characteristic precipitate in their identification tests with $K_4[Fe(CN)_6]$ is :
$Cu^{2+}, Fe^{3+}, Ba^{2+}, Ca^{2+}, NH_4^{+}, Mg^{2+}, Zn^{2+}$

On passing $H_2S$ gas,a black precipitate of $II$ group is obtained. The mixture may not contain:

Which compound gives a black color with $NH_4OH$?

Match List-$I$ with List-$II$ :

List-$I$ (Metal Ion)	List-$II$ (Group in Qualitative analysis)
$(a)$ $Mn^{2+}$	$(i)$ Group-$III$
$(b)$ $As^{3+}$	$(ii)$ Group-$IIA$
$(c)$ $Cu^{2+}$	$(iii)$ Group-$IV$
$(d)$ $Al^{3+}$	$(iv)$ Group-$IIB$

Choose the most appropriate answer from the options given below :

Consider the following reaction scheme: $D(\text{White ppt}) \xleftarrow{Na_2CO_3} A \xrightarrow[\text{in acetic acid}]{K_2CrO_4} B(\text{Yellow ppt})$ and $A \xrightarrow{dil.\ H_2SO_4} C(\text{White ppt})$. If $A$ is a metallic salt,then the white precipitate $D$ must be: