Final answer:
ADH would be considered a positive regulator of blood flow because it can function as a vasoconstrictor, leading to increased blood pressure and volume.
Step-by-step explanation:
ADH, or antidiuretic hormone, also known as vasopressin, plays a key role in regulating the amount of water reabsorbed by the kidneys, and it is also involved in the regulation of blood flow and blood pressure. When blood pressure is low, ADH acts to conserve water by promoting water reabsorption in the kidneys, and at high levels, ADH functions as a vasoconstrictor, which results in constricted blood vessels and increased blood pressure. Therefore, ADH would be considered a positive regulator of blood flow, as it works to increase blood pressure and blood volume when necessary.