The correct option is A chlorine
The electron affinity is a measure of the attraction between the incoming electron and the nucleus. Generally, E.A decreases down a group, but E.A of Cl is greater than E.A of F because of fluorine
is such a small atom, you are putting the new electron into a region of
space already crowded with electrons and there is a significant amount
of repulsion. This repulsion lessens the attraction the incoming
electron feels and so lessens the electron affinity. Therefore Cl has the highest electron affinity.
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