Final answer:
Acid Citrate Dextrose (ACD) prevents blood clotting by chelating calcium ions, which are necessary for the coagulation cascade.
Step-by-step explanation:
Acid Citrate Dextrose (ACD) is a solution used as an anticoagulant during blood collection and processing. Its function is to prevent clotting by chelating calcium ions which are essential for the coagulation cascade. Therefore, the correct answer to what ACD does is b. Prevents clotting. Like other anticoagulants such as EDTA and oxalates, citrates bind to calcium and prevent it from participating in the enzymatic conversion of prothrombin into thrombin, which is a crucial step in blood clot formation. By doing so, ACD ensures that the blood sample remains in a liquid state suitable for various laboratory analyses, including hematological and transfusion applications.