Which one of the following ores is best concentrated by froth floatation method?

In the context of the Hall-Heroult process for the extraction of Al, which of the following statements is false?

Which method of purification is represented by the following equation :
Ti (s) + 2I₂ (g) $$\buildrel {523K} \over \longrightarrow $$ TiI₄ (g) $$\buildrel {1700K} \over \longrightarrow $$ Ti (s) + 2I₂ (g)

Which of the following factors is of no significance for roasting sulphide ores to the oxides and not subjecting the sulphide ores to carbon reduction directly?