Final answer:
The purple-top tube contains an anticoagulant that binds calcium, using EDTA as the chelating agent. These tubes are used for hematological tests to prevent blood clotting. When both anti-A and anti-B antibodies cause agglutination, it indicates an AB blood type. So the correct answer is option (C).
Step-by-step explanation:
The tube that contains an anticoagulant that works by binding calcium is the Purple-top tube. The reason for this is that purple-top tubes generally contain EDTA, which acts as a chelating agent that binds to calcium ions, preventing blood from clotting. Therefore, when blood samples require full blood counts or other hematological tests where it is essential for the cells to remain in their natural state without clotting, purple-top tubes are the preferred choice.
In the context given, regarding the precipitation of calcium oxalate, an anticoagulant mechanism similar to the one described for purple-top tubes is at play. The anticoagulant salt of an oxalate ion binds the calcium, thus removing it from the plasma in the blood and preventing clot formation.
As for the blood type testing, visible agglutination in both the presence of anti-A and anti-B antibodies indicates that the patient has an AB blood type. This response is normal for individuals with AB blood type, as their blood contains both type A and type B antigens.