Which of the following statements is/are correct?

Options

A. The complex `CuCl_(4)^(2-)` exists but `CuI_(4)^(2-)` does not
B. A bidentate chelating ligand replaces two monodentate ligands locate in cis positions of square [planar complex.
C. A singly bidentate chelating ligand replaces two monodenate ligands located in trans positions of square planar complex.
D. `[Fe(CN)_(6)]^(3-)` is more stable than `[Fe(CN)_(6)]^(4-)`

Explanation

a. `Cu^(2+)` is reduced to `Cu^(+)` by `I^(-)` but not by `Cl^(-)`
`Cu^(2+)+I^(-)toCuI, CuI+3I^(-)to[CuI_(4)]^(3-)`
c. The trans positions are too distant for a bidenate ligand to span.
d. Fe (III) in `[Fe(CN)_(6)]^(3-)` has greater charge density than Fe(II) in `[Fe(CN)_(6)]^(4-)` hence the former thas greater stability than the latter.