Final answer:
The preferred anticoagulant for coagulation studies testing is Citrate because it effectively binds to calcium ions and prevents blood clotting, allowing for accurate testing of blood coagulation factors.
Step-by-step explanation:
The preferred anticoagulant for coagulation studies testing is B) Citrate. Anticoagulants are substances that prevent blood from coagulating, which is crucial during coagulation studies to analyze blood clotting times and other parameters effectively. Citrate binds to calcium ions in the blood and removes them from the coagulation process, thus preventing clot formation. This makes citrate an ideal choice for such testing, as proper coagulation testing requires an environment that closely resembles that of natural blood flow without the clotting factors being activated.