It can be inferred from the passage that which of the following is true of species of terrestial snakes that often need to assume a vertical posture
-they are more likely to be susceptible to circulatonry failure in vertical postures than are sea snakes
-they cannot counteract the pooling of blood in lower regions of their bodies as effectively as sea snkes can
-their hearts are less likely to be located at the midpoint of their bodies than is the case with sea snakes
-the blood pressure at their midpoint decreases significantly when they are tilted with their heads up