(a) Platinum, gold and silver are used to make jewellery because they are very lustrous. Also they are less reactive and do not corrode easily.

(b) Sodium, potassium and lithium are very reactive metal which react with the atmospheric moisture when kept in the open and produce fire as well. So, these are always kept immersed in kerosene oil to prevent their reaction with air and to prevent accidental fires.

(c) Although aluminium is a highly reactive metal, it is resistant to corrosion. This is because when aluminium metal react with oxygen present in air to form a protective layer of aluminum oxide on its surface. This oxide layer is very stable and makes the aluminium metal resistant to the action of air and water. Also, it is light in weight and good conductor of heat, hence it is used for making cooking utensils.

(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction because it is much easier to obtain metals from its oxide as compared to its sulphides and carbonates.