The correct order of second ionization potential of carbon, nitrogen, oxygen and fluorine is:-

The correct option is

C

O > F > N > C
Electronic configuration of element after removal of first electron
$O^{+}=1s^{2}2s^{2}2p^3$
$F^{+}=1s^{2}2s^{2}2p^4$
$N^{+}=1s^{2}2s^{2}2p^2$
$C^{+}=1s^{2}2s^{2}2p^1$
Second Period: C N O F

The second ionization potential of oxygen is more, as it acquires a half-filled stable electronic configuration so it requires a lot of energy to remove electrons from the oxygen. Hence it has the highest ionization energy.
So, the correct order of second ionization potential is O > F > N > C.