An aqueous solution of a mixture of two inorganic salts, when treated with dilute `HCl`, gave a precipiate (P) and filtrate (Q). The precipitate (P) was found to dissolve in hot water. The filtrate (Q) remained unchanged, when treated with `H_(2)S` in a dilute mineral acid medium. However, it gave a precipitate (R) With `H_(2)S` in an ammoniacal medium. The precipitate R gave a coloured solution (S), when treated with `H_(2)O_(2)` in an aqueous `NaOH` medium. The precipitate P containsA. `Pb^(2+)`B. `Hg_(2)^(2+)`C. `Ag^(+)`D. `Hg^(2+)`