Correct Answer:

Heparin

Solution : The correct option is Heparin.

Heparin is an anticoagulant that occurs naturally in the body. It inhibits the action of thrombin, an enzyme that transforms fibrinogen into fibrin, a protein that produces blood clots, by binding to antithrombin III. Antithrombin is a protein that prevents thrombin from converting fibrinogen into fibrin, a protein that produces blood clots.