Which of the following statement is wrong about the coordination number of central atoms:

A、If the ligands are all unidentate, the total ligand number is the coordination number of central atoms;

B、The total number of coordination atoms that directly coordinated with the central ions or atoms is their coordination number ;

C、In all coordination compound, the total ligand number is the number of the coordination number of central atoms;

D、The common coordination number is 6 and 4