What are the oxidation states of the transition metals in the following compounds?

i)
Sum of the oxidation states for the compound = 0
Oxidation state of each CO ligand = 0
Oxidation state of Cr = 0 - 6(0) = 0

ii)
Sum of the oxidation states for the compound = 0
Oxidation state of each ONO⁻ ligand = -1
Oxidation state of each bipy ligand = 0
Oxidation state of the SO₄²⁻ ion = -2
Oxidation state of Cr = 0 - 2(-1) - (-2) = +4 = IV

iii)
Sum of the oxidation states for the compound = 0
Oxidation state of the K⁺ ion = +1
Oxidation state of the O²⁻ ligand = -2
Oxidation state of each Cl⁻ ligand = -1
Oxidation state of Mo = 0 - (+1) - (-2) - 4(-1) = +5 = V

The answer: B. i) O; ii) IV; iii) V