The Correct choice is D. Fe + S = FeS
because, in nature Iron (Fe) and Sulphur (S) are found in mono - Atomic form. so, There will be 1 Fe atom reacting with 1 S atom to form FeS (Iron sulphide)
In the reactants Sb has oxidatin number 0 (because it is in its elemental form)
In the products Sb has oxidaton number +3.
Then Sb lost electrons which means it oxidized.
N just use a electronegativity table