Final answer:
A chelator is a substance that binds to metal ions such as calcium to remove them from solution, for instance, the hexadentate ligand EDTA, used in applications like water softening, anticoagulation, and food preservation. The correct option is (C)
Step-by-step explanation:
A chelator is a substance that binds to or chelates metal ions, such as calcium, to remove them from solution. The correct answer to the question of what a chelator is would be (C) a substance that binds to or chelates calcium ions to remove them from solution. Chelators like the hexadentate ligand EDTA are used to form very stable complexes with metal cations, which prevents these ions from reacting with other substances like soap. This property is beneficial in various applications, such as softening hard water, preventing blood coagulation by removing calcium from the blood, and preserving food by preventing metal-catalyzed reactions that can change food color.