What is the process of leaching also known as?

Which one of the following is true?

The methods $NOT$ involved in the concentration of ore are:
$A$. Liquation
$B$. Leaching
$C$. Electrolysis
$D$. Hydraulic washing
$E$. Froth flotation
Choose the correct answer from the options given below:

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 :

Which of the following ores can be concentrated by the froth flotation method?

What is leaching? Explain with an example.