How do we represent #(i)# represent the reduction of #"chlorate ion"#, #ClO_3^(-)#, to give #ClO_2#?

And #(ii)# the reduction of #SO_4^(2-)# to #S^(2-)#?

And #(iii)# the oxidation of #Mn^(2+)# to #MnO_2#?

And #(iv)# the oxidation of #Zn# to give #ZnCl_2#?