Which of the following statements is incorrect ?
A. In `K_(3)[Fe(CN)_(6)]` the ligand has satisfied only the secondary valency of ferric ion .
B. In `K_(3)[Fe(CN)_(6)`, the ligand has satisfied both primary and secondary valencies of ferric ion
C. In `K_(4)[Fe(CN)_(6)]` the ligand has satisfied both primary and secondary valencies of ferrous ion.
D. In `[Cu(NH_(3))_(4)]SO_(4)` the ligand has satisfied only the secondary valency of copper.
