a. It is a disproportionation reaction.
b. Cyanogen `(CN)_(2)` gets simultaneously reduced to `CN^(Θ)` ion as well as oxidised to cyanate ion.
c. oxidation number of `N` in `(CN)_(2)` is `-3` while that in `CN^(Θ)` is` -2` and in `CNO^(Θ)` is `-5`.
d. The reaction occurs in basic medium.