Answer:
The oxidation number of C in K2CO3 is +4. The oxidation number of O in K2CO3 is -2. The oxidation number of K in K2CO3 is +1.
The oxidation number of O in HIO is -2. The oxidation number of I in HIO is +1. The oxidation number of H in HIO is +1.
oxidation number of O in Na2SO4 is -2. The oxidation number of S in Na2SO4 is +6. The oxidation number of Na in Na2SO4 is +1.