Which one among the following pairs of ions cannot be separated by `H_2 S` in dilute hydrochloric acid?

Options

A. `Bi^(3+),Sn^(4+)`
B. `Al^(3+),Hg^(2+)`
C. `Zn^(2+),Cu^(2+)`
D. `Ni^(2+),Cu^(2+)`

Explanation

`Bi^(3+)` and `Sn^(4+)` are in the same group II of qualitative inorganic analysis , both of them will be precipitated as their respective sulphides.