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

In the isolation of metals, calcination is a process where the ore is heated strongly in the absence of air or in a limited supply of air. This step is crucial for removing volatile impurities and converting the ore into a more suitable form for reduction.

Let us consider common types of ores and what happens during calcination:

For carbonate ores, such as zinc carbonate (ZnCO₃) or limestone (CaCO₃), calcination causes decomposition. The reaction for zinc carbonate is:

Here, zinc carbonate decomposes to zinc oxide (a metal oxide) and carbon dioxide gas.

For hydrated ores, like bauxite (Al₂O₃·2H₂O), calcination removes water of hydration:

This yields aluminium oxide (a metal oxide).

For hydroxide ores, such as iron(III) hydroxide, calcination leads to decomposition:

This produces iron(III) oxide (a metal oxide).

Now, examining the options:

Option B: Metal carbonate - Calcination decomposes carbonates, so it does not result in a carbonate.

Option C: Metal sulphide - Sulphide ores are typically roasted (heated in excess air) to form oxides, not calcined to sulphides.

Option D: Metal hydroxide - Hydroxides decompose to oxides upon heating, so calcination does not yield hydroxides.

In all cases, calcination produces metal oxides. Hence, the correct answer is Option A.