Which of the following steps are involved in hydrometallurgical process ?

• A

  ${\mathrm{Cu}}_2\mathrm{S}+2{\mathrm{Cu}}_2\mathrm{O}⟶6\mathrm{Cu}+{\mathrm{SO}}_2$

• B

  ${\mathrm{CuFeS}}_2+2{\mathrm{H}}_2{\mathrm{SO}}_4⟶{\mathrm{CuSO}}_4+{\mathrm{FeSO}}_4+2{\mathrm{H}}_2\mathrm{S}$

• C

  ${\mathrm{Ag}}_2\mathrm{S}+2\mathrm{NaCN}⟶{\left[\mathrm{Ag}(\mathrm{CN}{)}_2\right]}^{\ominus }+{\mathrm{Na}}_2\mathrm{S}$

• D

  ${\mathrm{CuCO}}_3+{\mathrm{H}}_2{\mathrm{SO}}_4⟶{\mathrm{CuSO}}_4+{\mathrm{H}}_2\mathrm{O}+{\mathrm{CO}}_2$