$2BF_3 + 6NaH \xrightarrow{450 \ K} X_{(g)} + 6NaF$. Which of the following statements is \textbf{Incorrect} for $X$?

• A
  $X$ is readily hydrolysed by water to give a weak monobasic acid.
• B
  Back bonding is present in $X$.
• C
  In $X$,the maximum number of atoms in one plane is $6$.
• D
  $X$ burns with $O_2$ and gives sesquioxide.