Which step is involved in the extraction of $Pb$ from galena $(PbS)$?

Match the method of concentration of ore in Column $I$ with the ore in Column $II$.

$I$ (Method)	$II$ (Ore)
$(I)$ Magnetic separation	$a. Cu_2S$
$(II)$ Froth flotation	$b. FeCr_2O_4$
$(III)$ Gravity separation	$c. Al_2(SiO_3)_3$

Froth flotation method is used for the concentration of $.......$.

The pair of oxides,which can be leached out when powdered bauxite containing certain impurities is digested with a concentrated solution of $NaOH$ at $473-523 \ K$ temperature and $35-36 \ bar$ pressure,are:

Ores like magnetite or tungstates in tin ores are concentrated by

Which one of the following is not a method of concentration of ore?