(A) Froth floatation process used for the concentration of sulphide ore is based on the difference in wettability of different minerals. The metallic sulphide particles of ore are preferentially wetted by oil and the gangue particles by water.

(B) Froth floatation process used for the concentration of sulphide ore uses sodium ethyl xanthate, $C _2 H _5 OCS _2 Na$ as collector. Other examples of collector include ethyl xanthate and potassium ethyl xanthate. They attach themselves to the grains of mineral by polar groups so that minerals become water repellent and pass on into the froth.

(C) Froth floatation process used for the concentration of sulphide ore uses $NaCN$ as depressant in the mixture of $ZnS$ and $PbS$ when $ZnS$ forms soluble complex and $PbS$ forms froth. Other depressant used is $KCN$. Depressants depress the floating property of one of the components of the ore and help in the separation of different minerals present in the same ore.

Thus, all of the above statements are correct.