The correct answer is D. blood platelets.
Prothrombin is a protein that is converted to thrombin in the presence of calcium ions and thromboplastin. Thrombin then converts fibrinogen to fibrin, which forms a mesh that traps blood cells and forms a clot.
Lymphocytes are a type of white blood cell that helps the body fight infection. Erythrocytes are red blood cells that carry oxygen to the body’s tissues. Monocytes are a type of white blood cell that can become macrophages, which are cells that eat bacteria and other foreign particles.
Blood platelets are small, irregularly shaped cells that are essential for blood clotting. They are produced in the bone marrow and circulate in the blood. When a blood vessel is damaged, platelets stick to the damaged area and form a plug. This plug helps to stop the bleeding.
I hope this helps!