Which of the following statements are correct?

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

b.  Copper matte contains Cu2S and ZnS.

c.  The solidified copper obtained from the reverberatory furnace has a blistered appearance due to the evolution of SO2 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)