Element not showing variable oxidation state is :

Among the halogens:

- Chlorine shows oxidation states: -1, 0, +1, +3, +5, +7 (variable)

- Bromine shows oxidation states: -1, 0, +1, +3, +5, +7 (variable)

- Iodine shows oxidation states: -1, 0, +1, +3, +5, +7 (variable)

- Fluorine shows only oxidation state: -1 (and 0 in $$F_2$$). Since fluorine is the most electronegative element, it cannot show positive oxidation states.

Fluorine does not show variable oxidation state. The answer corresponds to Option (4).