Which one of the following oxides is a neutral oxide?

Oxides can be classified as acidic, basic, amphoteric, or neutral based on their acid-base characteristics.

$CO$ (Carbon monoxide) is a neutral oxide because it neither reacts with acids nor with bases to form salts.

$CO_2$ is an acidic oxide as it reacts with water to form carbonic acid.

$Na_2O$ and $MgO$ are metallic oxides, which are basic in nature.

Other common examples of neutral oxides include $N_2O$ and $NO$.

Answer: $CO$