The correct option is C Potassium hexacyanidoferrate(III)
IUPAC naming of coordination compound:
The names of coordination compounds are derived by the following principles of nomenclature,
1. The cation is named first in both positively and negatively charged coordination entities.
2. The ligands are named in an alphabetical order before the name of the central atom/ion.
Also, the number of cations or anions is not denoted in the name of a coordination compound. So, in this case the counter ion is named as potassium and not tripotassium. CN is an anionic ligand and should end with -o. with the correct name being cyanido or cyanido-C.
Hence (c) is the correct option