Which of the Following Mechanisms Are Used to Regulate Blood

Multiple Choice

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 smooth muscle in the walls of arterioles
III.opening or closing precapillary sphincters

A) only I and II
B) only I and III
C) only II and III
D) I, II, and III