Final answer:
The false statement is that we stop drinking when osmotic pressure is restored; in truth, the body signals the need to drink before full restoration of osmotic balance to prevent dehydration.
Step-by-step explanation:
Among the given statements, the one which is false is: a. We stop drinking when osmotic pressure is restored and not before. In reality, drinking water is a voluntary action and the body signals the need to drink well before osmotic pressure is fully restored.
Adding salt to the body's extracellular fluids would indeed increase osmotic thirst, as the solute concentration outside the cells would increase, leading to water moving out of the cells to achieve osmotic balance, thus triggering thirst. Both vasopressin and angiotensin II do indeed constrict blood vessels; this is a mechanism to retain water and maintain blood pressure. And hypovolemic thirst, which is thirst prompted by reduced blood volume, typically does increase the desire for salty water since salty water helps to restore the solute balance as well as the volume in the blood and extracellular fluids.