c
Ionic product in the solution \(=10^{-3} \times 10^{-16}=10^{-19}\). The metal sulphide having the lowest solubility will precipitate first provided the ionic product is higher than the \(K_{\text {sp. }}\). Here, all salts are of the same valence type. So, the sulphide having the lowest \(K_{s p}\) value will precipitate first provided \(K_{s p}\,<\,10^{-19}\). HgS has the lowest \(K _{\text {sp }}\) value \(\left(10^{-54}\right)\), so it will precipitate first.