Which of the following mechanisms are used to regulate blood pressure in the closed circulatory system of vertebrates? I.changing the force of heart contraction II.constricting and relaxing sphincters in the walls of arterioles III.adjusting the volume of blood contained in the veins IV.synthesizing new capillaries
A)only I and II B)only I and III C)only II and III D)I, II, and III E)I, II, and IV