Which of the following statements about complexes that form between metals, Mn⁺, and EDTA in aqueous solutions is true?
a. Metal-EDTA complexes have an equilibrium concentration that is independent of pH.
b. Metal-EDTA complexes are usually highly colored.
c. Metal-EDTA complexes are often in 2:1 stoichiometry
d. Metal-EDTA complexes are less stable than the corresponding metal-ammine complexes
e. The presence of other complexing ligand in solution affects the equilibrium concentration of metal-EDTA complexes.