Element 'X' forms an oxide with the formula X 2 O 3 which is a solid with high melting point. 'X' would most likely be placed in the group of the Periodic Table…

(c) Al

The formula X₂O₃ indicates that the element 'X' forms a trivalent oxide. Thus, 'X' has a valency of 3 like that of Al (Valency of Na, Mg and Si are 1, 2 and 4, respectively). In Group 13, the elements typically form oxides with the general formula X₂O₃, where 'X' represents the element. The oxides of Group 13 elements, such as Al₂O₃ (aluminum oxide), have high melting points due to the strong ionic bonds between the metal cations and the oxide anions.