The hybridisation of the central atom of $BF_3$,$SnCl_2$,and $HgCl_2$ respectively is:

Why does boron trifluoride behave as a Lewis acid?

$sp^3d^2$ hybridization is not displayed by

What is the hybridization state of the central atom in the conjugate base of $NH_4^{+}$ ion?

Which of the following does not have $sp^3$ hybridization?

Consider the following statements for $\dot{CH_3} = X$ and $\dot{CF_3} = Y$:
$I$. When $X$ dimerises,the bond angle decreases.
$II$. When $X$ dimerises,the bond angle increases.
$III$. In the $X-Y$ molecule,the $C-C$ bond length is less than that in the $Y-Y$ molecule.
$IV$. The bond angle in $X$ is greater than that in $Y$.