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

Solution :
Froth floatation method is mainly applicable for sulphide ores.
$$\eqalign{ & \left( 1 \right)\,{\text{Malachite ore }}:\,Cu{\left( {OH} \right)_2}.CuC{O_3} \cr & \left( 2 \right)\,{\text{Magnetite ore }}:\,F{e_3}{O_4} \cr & \left( 3 \right)\,{\text{Siderite ore }}:\,FeC{O_3} \cr & \left( 4 \right)\,{\text{Galena ore }}:\,PbS\,\left( {{\text{Sulphide}}\,{\text{Ore}}} \right) \cr} $$