Which of the following test is shown here?

Ans. (a) coagulase test.* The image shows Coagulase test. The Upper tube is inoculated with Staphylococcus aureus; lower tube is inoculated with Staphylococcus epidermidis. Arrow points to clotted plasma formed by coagulase produced by Staphylococcus Aureus.* Coagulase reacts with prothrombin in the blood. The resulting complex is called staphylothrombin, which enables the enzyme protease to convert fibrinogen, a plasma protein produced by the liver, to fibrin. This results in clotting of the blood. Coagulase is tightly bound to the surface of the bacterium S. aureus and can coat its surface with fibrin upon contact with blood. The fibrin clot may protect the bacterium from phagocytosis and isolate it from other defenses of the host.Image source- style="font-family: Times New Roman, Times, serif">