Which one among the pairs cannot be separated by H2S in dilute HCl?

Cu^2+, Zn^2+

Bi^3+, Sn^4+

Al^3+, Hg^2+

None of these

H₂S in dilute HCl is used to separate metal ions based on their solubility as sulfides.

Bi³⁺ and Sn⁴⁺ do not separate easily.

Because they both form insoluble sulfides under similar conditions.