Which of the following statements is incorrect ?
A. In K₃[Fe(CN)₆] the ligand has satisfied only the secondary valency of ferric ion .
B. In K₃[Fe(CN)₆, the ligand has satisfied both primary and secondary valencies of ferric ion
C. In K₄[Fe(CN)₆] the ligand has satisfied both primary and secondary valencies of ferrous ion.
D. In [Cu(NH₃)₄]SO₄ the ligand has satisfied only the secondary valency of copper.