The correct option is D I<Br<F<Cl
Put differently, we are looking at the electron affinity Eea values. The electron affinity of an atom or molecule is defined as the amount of energy released or spent when an electron is added to a neutral atom or molecule in the gaseous state to form a negative ion.
Generally as we move down the group, electron affinity goes on decreasing. But due to small size of F atom, there is more repulsion between existing electron and incoming electron. So, the electron affinity becomes less than Cl atom.
Hence, the correct order is I<Br<F<Cl