Which of the following substances acts as a collector in the froth floatation method?

In the extraction of $Al$,the chemical used in the Serpek process is:

Given below are two statements :
Statement $I :$ Sphalerite is a sulphide ore of zinc and copper glance is a sulphide ore of copper.
Statement $II :$ It is possible to separate two sulphide ores by adjusting proportion of oil to water or by using 'depressants' in a froth flotation method.
Choose the most appropriate answer from the options given below :

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	$c. Al_2(SiO_3)_3$

Which of the following ores cannot be concentrated by the froth flotation method?

In the leaching method,bauxite ore is digested with a concentrated solution of $NaOH$ that produces $X$. When $CO_2$ gas is passed through the aqueous solution of $X$,a hydrated compound $Y$ is precipitated. $X$ and $Y$ respectively are