The following are the differences between exclusive and non-exclusive adsorption, which of the statement is correct?

A、Non-exclusive adsorption mainly occurs in the diffusion layer and exclusive adsorption occurs in the inner layer;
B、When adsorption occurs, the pH value of the exclusive adsorption must be greater than the isoelectric point, and there is no requirement for non-exclusive adsorption;
C、Metal ions act as countra-ions in exclusive adsorption and as coordination ions in non-exclusive adsorption;
D、Cation exchange adsorption mainly occurs in exclusive adsorption, while ligand exchange adsorption occurs in non-exclusive adsorption