Which of the following statements are correct?

a.  A depressant prevents certain types of particles to come to the froth.

b.  Copper matte contains ${\mathrm{Cu}}_{2}\mathrm{S}$ and $\mathrm{ZnS}$.

c.  The solidified copper obtained from the reverberatory furnace has a blistered appearance due to the evolution of ${\mathrm{SO}}_{2}$ during the extraction.

d.  Zinc can be extracted by self-reduction.

Choose the correct option
1. (a, b)
2. (b, c)
3. (c, d)
4. (a, c)

Correct statements are
(i) A depressant prevents certain type of particle to come to the froth. e.g., NaCN is added as a depessant during separation of PbS and ZnS.
(ii) The Solidified copper obtain from reverberatory furnace has blistered appearance due to evolution of ${\mathrm{SO}}_{2}$ during the extraction.
(b) and (d) are incorrect statements, and can be correctly stated as
(iii) Copper matte contains ${\mathrm{Cu}}_{2}\mathrm{S}$ and $\mathrm{FeS}$.
(iv) Zinc can be extracted by reduction of $\mathrm{ZnO}$ with carbon.