An element $A$ forms two oxides $AO$ and $AO_2$. The oxide $AO$ is neutral,whereas the oxide $AO_2$ is acidic in nature. Would you call element $A$ a metal or a non-metal?

(B) Element $A$ is a non-metal because non-metal oxides are typically acidic or neutral in nature.
$AO$ (e.g.,$CO$ - Carbon monoxide) is a neutral oxide.
$AO_2$ (e.g.,$CO_2$ - Carbon dioxide) is an acidic oxide.
Since metals generally form basic oxides,the formation of neutral and acidic oxides confirms that $A$ is a non-metal.