Which substances are used as stabilizers in the froth flotation process?

For the purification of alumina,the modern processes most useful when $(i)$ the impurity present is a lot of iron oxides and $(ii)$ the impurity present is a lot of silica,are:

The froth floatation process used for the concentration of sulphide ore:

Froth floatation process is used for the concentration of

Wolframite ore is separated from tinstone $(SnO_2)$ by which of the following processes?

Which one of the following ores is best concentrated by froth floatation method?