Down group 17 the electron gain enthalpy generally becomes less negative ($ceCl$ -349, $ceBr$ -325, $ceI$ -295), yet $ceF$ (-328) is less negative than $ceCl$. Which statement correctly accounts for this?

1. AFluorine has a larger atomic radius than chlorine, so it holds the extra electron weakly
2. BThe very small $2p$ subshell of $ceF$ gives strong inter-electronic repulsion that offsets its smaller size and stronger nuclear attraction
3. CFluorine has a half-filled $2p$ subshell, so it resists gaining an electron
4. DFluorine has a lower nuclear charge than chlorine, so its attraction for the extra electron is smaller