Sodium Thiosulfate,Na₂S₂O₃,is Used as a "Fixer" in Black and White $\to$

Sodium thiosulfate,Na₂S₂O₃,is used as a "fixer" in black and white photography.Identify the reducing agent in the reaction of thiosulfate with iodine.
2S₂O₃^2-(aq) + I₂(aq) $\to$ S₄O₆^2-(aq) + 2I^-(aq)

A) I₂(aq)
B) I-(aq)
C) S₂O₃^2-(aq)
D) S₄O₆^2-(aq)
E) S₂O₃^2-(aq) and I^-(aq)