Which one of the following oxides is neutral ?

Oxides can be basic, acidic, amphoteric, or neutral. In the case of acidic oxides, it forms an acid when it dissolves in water. In the case of basic oxide, it forms the base in water. In the case of neutral oxide, there is no such acidic or basic property. In the case of amphoteric both acidic and basic property is present. Generally, metals form a basic oxide and non-metals form an acidic oxide, now from left to right of the periodic table metallic character decreases. Therefore, the acidity of oxide increases. Among the given oxides, CO is the neutral oxide. SnO₂ and ZnO are amphoteric and