An aqueous solution of a substance gives a white percipitate on treatment with dil ,HCI which dissolves on heating .When `H_(2)S` is passed through the hot acidinbg solution a black precipitate is obtained .The substances are not :
A. `Hg_(2)^(2+)` salt
B. `Cu^(2+)` salt
C. `Ag^(o+)` salt
D. `Pb^(2+)` salt