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

In the isolation of metals, the calcination process usually results in the metal oxide.

The calcination procedure commonly yields metal oxide when metals are isolated. Metal oxides and carbon dioxide are produced during the decomposition of carbonate ores. The reaction is as follows:

${\mathrm{ZnCO}}_3\stackrel{\mathrm{\Delta }}{⟶}\mathrm{ZnO}\left(\mathrm{s}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right)$

Hence, option A is correct.