A metal gives two chlorides `A` and `B`. `A` gives black precipitate with `NH_4OH` and `B` gives white. With `KI`, `B` gives a red precipitate soluble in excess of `KI`. `A`and `B` are respectively:

Options

A. `HgCl_2` and `Hg_2Cl_2`
B. `Hg_2Cl_2` and `HgCl_2`
C. `HgCl_2` and `ZnCl_2`
D. `ZnCl_2` and `HgCl_2`

Answer

B