Which is true for an element X ~present in the~ 13 ^ th & group of...

The elements of group$- 13$ of the periodic table are solids (examples: $B, Al$, etc.) at room temperature.

They have a common oxidation state of $+ 3$ (as they have three valence electrons in the outermost shell).
So, they form an oxide of formula ${X}_{2}{O}_{3}$ from the ions $X^{3 +}$ and $O^{2 -}$.~

It forms a metal chloride of formula ${XCl}_{3}$~and dimer ${X}_{2}{Cl}_{6}$& as the octet state, which accounts for stability& is not fulfilled for the metal in the monomer.