Question

In the following reaction sequence, the correct structure(s) of X is (are)

^{$$\begin{gathered} X\underset{2)Nal ,M{e}_{2}CO \\ 3)Na{N}_3 , HCONM{e}_2}{\overset{1)PB{r}_{3,}E{t}_{2}O}{\to }} \end{gathered}$$}