Which of the following on thermal decomposition yields a basic as well as acidic oxide?

Which of the following reactions is an example of calcination?

The main function of roasting is

The role of calcination in metallurgical operations is

Choose the correct code regarding the Roasting process.
$I$. It is the process of heating ore in air to obtain the oxide.
$II$. It is an exothermic process.
$III$. It is used for hydrated oxide and oxysalt ore.
$IV$. It is used after the concentration of ore.

In the isolation of metals,the calcination process usually results in: