What Is the Purpose of the Sphincters Where the Arterioles

What is the purpose of the sphincters where the arterioles branch into the capillary beds?

A) To slow down blood flow so the capillaries don't burst under pressure
B) To control blood flow to different areas of the body depending on activities
C) To speed up blood flow into the capillary bed for faster oxygen exchange
D) To block blood from coming back out of the capillary bed too quickly to allow for more complete diffusion of oxygen
E) They remove carbon dioxide from blood passing through.