Consider the following statements: Roasting is carried out to
a. Convert sulphide to oxide and sulphate
b. Remove water of hydration
c. Melt the ore
d. Remove arsenic and sulphur impurities Of these statements:

The removal of the excess sulphur contained in sulphide ores by heating in an excess of air is called roasting. The concentrated sulphide ore is heated in reverberatory furnace, below its melting point or fusion temperature in the presence of an excess of air with or without the addition of an external substance. 
In roasting definite chemical like oxidation, chlorination etc. take place but in calcination does not occur any major chemical changes.

Advantages of Roasting :
(i) Excess of sulphur is removed as volatile oxide. 
(ii) The metal sulphide is converted into metal oxide and sulphate. 
(iii) Impurities of arsenic and antimony are removed as their volatile oxides