Which substance is used as a froth stabilizer in the froth flotation process?

Which of the following is used as a stabilizer during the concentration of sulphide ores?

During initial treatment,preferential wetting of ore by oil and gangue by water takes place in

Explain the froth flotation process.

Leaching of $Ag_2S$ is carried out by heating it with a dilute solution of

Select the correct option regarding the method of separating two sulfide ores by the froth flotation process.
$(1)$ The ratio of water and oil is chosen appropriately.
$(2)$ Some depressants are used for this process.
$(3)$ $HCN$ is a depressant for a mixture of $ZnS$ and $PbS$.
$(4)$ By using a suitable depressant for a mixture of $ZnS$ and $PbS$,only $PbS$ comes up with the froth.