Which of the following is the strongest reducing agent?

For the reactions $(A) \ S^{2-} + 4H_2O_2 \rightarrow SO_4^{2-} + 4H_2O$ and $(B) \ Cl_2 + H_2O_2 \rightarrow 2HCl + O_2$,which statement is correct?

In the reaction $HAsO_2 + Sn^{2+} \to As + Sn^{4+} + H_2O$,the oxidizing agent is:

Which of the following mixtures is chromic acid?

Which of the following,after reacting with $KI$,does not liberate iodine?

Which of the following is not a reducing agent?