Statement A
Ethane−1,2−diamine is a chelating agent as it contains two coordinating sites that are two nitrogen atoms which donate their lone pairs of electrons and can form a 5-membered ring with the metal ion.

Statement B
Based on Hall-Heroults process-
The Hall-Heroult process is widely used in the extraction of aluminium. In Hall-Heroults process, pure Al2O3is mixed with CaF2orNa3AlF6. This results in lowering the melting point of the mixture and increases its ability to conduct electricity. A steel vessel with a lining of carbon and graphite rods is used.
Statement C
Cyanide ion is used as ligand for leaching of silver.
The cyanide process, which is also known as the Macarthur-forest process, is widely used in extracting gold or silver from the ores by dissolving them in a dilute solution of potassium cyanide or sodium cyanide.
Statement D
[Rh(PPh3)3Cl] Wilkinson's catalyst
Statement E
Ca++ ion forms more stable complex with EDTA
Hence option C is the answer.