The correct options are
A treating aqueous solution of HgCl2 with excess of stannous chloride
C placing copper metal in aqueous solution of HgCl2
Mercuric chloride is converted into mercury by
(A) placing copper metal in aqueous solution of HgCl2
2Cu+HgCl2→2CuCl+Hg
(B) treating aqueous solution of HgCl2 with excess of stannous chloride.
Mercuric chloride oxidses stannous chloride to stannic chloride . It itself is reduced to mercurous chloride.
2HgCl2+SnCl2→Hg2Cl2+SnCl4
Mercurous chloride is reduced to metallic mercury (grey) when it reacts with excess of stannous chloride.
Hg2Cl2+SnCl2→2Hg↓SnCl4