The möst unlikely representation of resonance structures of fluorobenzene is:

How many lone pairs of electrons are there in the given compound?

Decreasing order of $+ \mathrm{M}$-effect of given groups is :

$\left(\mathrm{I}\right)-{\mathrm{NR}}_2$  $\left(\mathrm{II}\right) -\mathrm{OCOR}$ $\left(\mathrm{III}\right) - \mathrm{NHCOR}$ $\left(\mathrm{IV}\right)-\mathrm{Ph}$

Decreasing $- \mathrm{m}-$power of given group is :

$\left(\mathrm{I}\right)-\mathrm{COOH}$ $\left(\mathrm{II}\right)-{\mathrm{NO}}_2$   $\left(\mathrm{III}\right) -\mathrm{CHO}$  $\left(\mathrm{IV}\right)-{\mathrm{CONH}}_2$