$Mn^{2+}$ can be converted into $Mn^{7+}$ by reacting with

Which of these is a reducing agent?

When ammonia is passed over heated copper oxide,metallic copper is obtained. The reaction shows that ammonia is

$Br^{-}$ is converted into $Br_2$ by using:

$(A) \ HOCl + H_2O_2 \rightarrow H_3O^{+} + Cl^{-} + O_2$
$(B) \ I_2 + H_2O_2 + 2 OH^{-} \rightarrow 2 I^{-} + 2 H_2O + O_2$
Choose the correct option.

$A$ sulphur-containing species that can not act as a reducing agent is