The correct option is D All of these
We have encountered the anomalous behavior of Nitrogen among the group 15 elements. If you took the hint, it is obvious that +3 and +5 oxidation states are the recurring theme among group 15 elements. Let us try and answer this question purely from what we know already, shall we?
We know that both Lithium and Magnesium form nitrides when they are burnt in air.
3Mg+N2→Mg3N2
Sodium also forms a Nitride - Na3N
Here, the nitride ion is N3−. Let us take Mg3N2. Alkaline earth metal exists as Mg2+ ions. We know that in ionic alkaline earth metal compounds, they tend to have +2 oxidation state. Let the oxidation state of Nitrogen be y.
Overall the molecule is neutral, so we have
3(+2) + 2(y) = 0
Solving, the oxidation state of N atom in Magnesium Nitride is y = -3.
Hence the option D is the most appropriate!