The set of correct statements is:
(i) Manganese exhibits \( +7 \) oxidation state in its oxide.
(ii) Ruthenium and Osmium exhibit \( +8 \) oxidation in their oxides.
(iii) Sc shows \( +4 \) oxidation state which is oxidizing in nature.
(iv) Cr shows oxidizing nature in \( +6 \) oxidation state.