$$\begin{gathered} A molecule which CANNOT exist theoretically is \\ a) {\mathrm{SF}}_4 \\ b) {\mathrm{OF}}_2 \\ c) {\mathrm{OF}}_4 \\ d) {\mathrm{O}}_2{\mathrm{F}}_2 \end{gathered}$$

OF₄ is most unlikely to be possible because fluorine is highly electronegative element . thus attract shared pair of electron towards its self causing oxygen atom suffer distorment . more over her oxygen atom is supposed to form two cordination bond with any two fluorine atoms which is unlikely to be possible.