Answer:
C. A Roman numeral placed after the transition metal identifies its
oxidation state.
Explanation:
A. A superscript on the transition metal identifies its oxidation state
in the formula.
This is wrong! Superscript are usually not written in formula of compound and for those that have superscripts, it refers to the oxidation number of the compound as a whole.
B. The subscript of the transition metal in the formula identifies its
oxidation state.
This is wrong! Subscripts shows how many atoms of the element is present.
C. A Roman numeral placed after the transition metal identifies its
oxidation state.
This is correct! Examples include; manganese (II) oxide, Potassium manganate (VII) etc
D. The total charge of the negative ion identifies the oxidation state
of the transition metal.
This is wrong! Because there are cases of other metals or cations being present in the compound aside the transition metal