[Fe (CN)6]4- is called as _.

Explanation

Option A: Complex compound, is a broader term that can refer to any compound that contains a complex ion, including both cationic and anionic complexes.Option B: Transition element ion, is a term that refers to any ion of a transition metal element. While Fe2+ is a transition metal ion, [Fe(CN)6]4- is a complex ion that contains a transition metal ion.Option C: Anion, is a term that refers to any negatively charged ion. While [Fe(CN)6]4- is an anion, it is specifically a complex anion due to the presence of the central metal ion and surrounding ligands.Option D: A complex ion is an ion comprising one or more ligands attached to a central metal cation (typically a transition metal) with a dative covalent bond. The number of lone pairs of electrons that a cation can accept is known as the coordination number of the cation.