Read the following statements and choose the correct option: (1) Ca²⁺ is necessary for blood coagulation. (2) Coagulation in blood vessel is prevented during normal condition by heparin. (3) Clotting of blood involves changes of fibrinogen to fibrin by thrombin. (4) Blood clotting involves a cascading process involving a number of factors, in which one active form always activates the next.