(i) InVOSO4,V′′ is in +4 oxidation state.
So it act as oxidising agent.
(ii) Cr2O3 is an amphoteric oxide.
(iii) InRuO4, ′Ru′ is in +8 oxidation state. So it act as oxidising agent.
(iv) Red colour of ruby is due to the presence of Cr+3 ions in Al2O2.