According to the passage one reason that the distribution of boold in the sea snake changes little while the creature remains in the ocean is that
-the heart of the sea snake tends to be located near the center of its body
-pressure gradients in the water surrounding the sea snake counter the effects of vertical pressure graduents within its boold vessels
-the sea snake assumes a vertical posture less frequently than do the terrestrial and the arboreal snake
-the sea snake often relies on waves of muscle contractions to help move boold from the torso to the head