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

The froth-floatation method is used specifically for the concentration of sulfide ores. Among the choices:Magnetite is an oxide ore (${\text{Fe}}_3{\text{O}}_4$).Malachite is a carbonate ore (${\text{CuCO}}_3\cdot \text{Cu}(\text{OH}{)}_2$).Galena is a sulfide ore ($\text{PbS}$).Cassiterite is an oxide ore (${\text{SnO}}_2$).
Thus, Galena is the correct answer.