Final answer:
When anticoagulated blood is centrifuged, platelet-rich plasma (option a) goes to the top of the tube. This plasma is the lightest component and it contains water, antibodies, and coagulation factors, contrasting with serum which lacks coagulation factors.
Step-by-step explanation:
When anticoagulated blood is centrifuged, the component that goes to the top of the tube is platelet-rich plasma. Centrifugation involves spinning the blood at high speeds, which separates its components based on density. The denser components, including red blood cells and white blood cells, move towards the bottom of the centrifuge tube. Sitting atop these cells is a layer known as the buffy coat, comprised of white blood cells and platelets. However, the lightest component, the plasma, rises to occupy the uppermost portion of the tube, appearing as a pale, straw-colored fluid and making up about 55% of the blood. This plasma includes water, various substances required for maintaining bodily functions, as well as antibodies and coagulation factors.
On the other hand, serum is the liquid component of the blood that remains after clotting has occurred and therefore does not contain the clotting factors. When centrifuged, the plasma which contains the clotting factors is at the top, whereas the serum would only be obtained after the removal of these factors.