Ans. is 'b' i.e., Vasoconstriction Hemostasiso Hemostasis is a physiological process where by bleeding is halted, thus protecting the integrity' of the vascular system after tissue injury.o It is responsible for minimizing blood loss,o It is commonly referred to as stoppage of bleeding,o The hemostatic mechanisms have several functions : -1. Maintain blood in fluid state while circulating within the vascular system.2 Arrest bleeding at the site of injury by formation of hemostatic plug.3. Ensure the removal of hemostatic plug when healing is complete.o The components of normal hemostasis include: -Blood vessels (endothelium)PlateletsPlasma coagulation factors and their inhibitors.Fibrinolytic system.o When a blood vessel is injured, several steps occur in hemostasis at the site of injury': -Vasoconstrictiono After initial injury, there is a brief period arteriolar vasoconstriction, minimizing vessel diameter and stowing bleeding.o This is due to reflex neurogenic mechanism and augmented by a potent endothelium derived vasoconstrictor endothelin.o However this effect is transient, bleeding would resume if there will no activation of platelet and coagulation system.Primary hemostasiso Endothelial injury exposes highly thrombogenic subendothelial extracellular matrix which allows the platelets to bind (adhere) with collegen of ECM.o Binding of platelets activates these cells and platelets release secretory' granules.o These secretory' products (from secretory granules) recruite additional platelets to form primary hemostatic (platelet plug).Secondary hemostasiso Coagulation system is activated and thrombin is generated,o Thrombin converts fibrinogen to fibrin.o Ultimately these events forms an ireversibly fused mass of platelets, thrombin RBCs and fibrinogen - Definitive secondary hemostatic plug.Repair of v essels and dissolution of cloto The clot attracts and stimulates the growth of fibroblast and smooth musc le cells within the vessel wall, and begins repair process.o At this stage fibrinolytic system is also activated, resulting in dissolution of the clot.