Match the metal in List-I with the key step of its extraction in List-II. List-I: (P) silver from argentite ore, Ag2S; (Q) copper from copper…

(P) Silver sulphide is leached with dilute aqueous $\mathrm{NaCN}$ in air: $\mathrm{Ag_2S+4CN^-\to2[Ag(CN)_2]^-+S^{2-}}$; the complex is then treated with zinc: $\mathrm{Zn+2[Ag(CN)_2]^-\to[Zn(CN)_4]^{2-}+2Ag}$ $\Rightarrow$ 4.
(Q) Roasted copper matte contains $\mathrm{Cu_2S}$ and $\mathrm{Cu_2O}$, which react by self (auto) reduction in the Bessemer converter: $\mathrm{2Cu_2O+Cu_2S\to6Cu+SO_2}$ $\Rightarrow$ 2.
(R) Pure alumina dissolved in molten cryolite ($\mathrm{Na_3AlF_6}$) with $\mathrm{CaF_2}$ is electrolysed in the Hall-Heroult process $\Rightarrow$ 1.
(S) Titanium is obtained by the Kroll process, $\mathrm{TiCl_4+2Mg\to Ti+2MgCl_2}$, under inert argon since $\mathrm{Ti}$ forms nitride and oxide with air and carbon reduction gives carbide $\Rightarrow$ 3.
(5) is a distractor; none of the four metals is obtained by simple carbon reduction in a blast furnace (that is used for iron). Correct code: P→4, Q→2, R→1, S→3.