Thiosulphate reacts differently with iodine and bromine in the reactions given below:
$2 S_2 O_3^{2-} + I_2 \rightarrow S_4 O_6^{2-} + 2 I^{-}$
$S_2 O_3^{2-} + 4 Br_2 + 5 H_2 O \rightarrow 2 SO_4^{2-} + 8 Br^{-} + 10 H^{+}$
Which of the following statements justifies the above dual behaviour of thiosulphate?

• A
  Bromine undergoes oxidation and iodine undergoes reduction by iodine in these reactions
• B
  Thiosulphate undergoes oxidation by bromine and reduction by iodine in these reactions
• C
  Bromine is a stronger oxidant than iodine
• D
  Bromine is a weaker oxidant than iodine