Answer
a.
Work Step by Step
Option b. is incorrect. Fibrinogen is a factor in blood clot formation.
Option c. is incorrect. Prothrombin is the protein precursor to thrombin, an enzyme involved in blood clotting.
Option d. is incorrect. Thrombin is the enzyme responsible for the formation of a blood clot. It is the converted form of prothrombin. Thrombin acts on fibrinogen, transforming it into sticky filaments called fibrin that trap blood cells so that they don't escape from the injured area.
Option a. is correct. Hemoglobin is a protein in red blood cells that binds to oxygen. Hemoglobin contains iron, which gives red blood cells their red color.
