Step-by-step explanation:
Ionization energy refers to the minimum amount of energy required to remove the valence electron of an isolated neutral gaseous atom or molecule. Generally, ionization energy increases from left to right across the periodic table.
This means that the ionization energy of Carbon would be smaller than that of Fluorine. The reason for this is due to the smaller effective nuclear charge.
The effective nuclear charge and the atomic size are two factors that ionization energy depends on.
The correct option is;
IV. The effective nuclear charge of carbon is smaller, so the valence electrons feel a weaker pull from the nucleus.