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_(2)Cl_(2)`
B. `Hg_(2)Cl_(2)` and `HgCl_(2)`
C. `HgCl_(2)` and `ZnCl_(2)`
D. `ZnCl_(2)` and `HgCl_(2)`

Answer

B