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

Which of the following ores is concentrated by the process of leaching?

When $ZnS$ and $PbS$ minerals are present together,then $NaCN$ is added to separate them in the froth floatation process as a depressant,because

Sulphide ores of metals are usually concentrated by froth floatation process. Which one of the following sulphide ores offers an exception and is concentrated by chemical leaching?

In the leaching of alumina from bauxite,the ore impurity expected to leach out in the process by reacting with $NaOH$ is:

Which method is used for the concentration of iron pyrites ore?