Which principle is involved in magnetic separation?

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:

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 :

In the process of extracting alumina from bauxite,bauxite is concentrated by $......$.

In the froth floatation process for the purification of ores,the ore particles float because

The ore that is concentrated by froth floatation process is