To determine which oxide is most acidic, we need to consider the nature of the oxides of Group 2 elements (alkaline earth metals).$\\$The oxides given are:$\\$• $$BaO (Barium oxide)$\\$• $$BeO (Beryllium oxide)$\\$• $$MgO (Magnesium oxide)$\\$• $$CaO (Calcium oxide)$\\$The acidity or basicity of an oxide is influenced by the metal's position in the periodic table.$\\$In general, oxides of metals become more basic as we move down a group in the periodic table.$\\$Conversely, oxides of metals become more acidic as we move up a group.$\\$Let's analyze each oxide:$\\$• $$BaO, CaO, and MgO are basic oxides. They react with acids to form salts and water.$\\$• $$BeO is an exception among the Group 2 oxides. It is amphoteric, meaning it can react with both acids and bases.$\\$The amphoteric nature of BeO indicates that it has some acidic character, unlike the other basic oxides.$\\$Therefore, BeO is the most acidic oxide among the given options.$\\$Thus, the correct answer is Option 2: BeO.