Vasopressin is related to
A. Conservation of water
B. Quick digestion
C. Dilution of urine
D. Slow heartbeat

Hint: Vasopressin is generally synthesised by the hypothalamus and is transported axially to the neurohypophysis. They are stored in the posterior pituitary. It is a polypeptide hormone and it is released by the stimulation in raising the osmolality of the plasma.

Complete answer:
Vasopressin is an Anti-Diuretic Hormones secreted by the posterior pituitary gland and acts on the nephron tubules which increase the reabsorption of water and thereby decreasing water content in urine while increasing that of blood. The increase in water concentration in the blood raises blood volume and blood pressure which makes the urine concentrated. It regulates the tonicity of body fluids and in response to hypertonicity and causes the kidneys to reabsorb solute-free water and return it to the circulation from the tubules of the nephron, thus returning the tonicity of the body fluids toward normal.
The main function of vasopressin is to help in the reabsorption of water by the renal tubules. In the distal tubules, water is reabsorbed with the help of vasopressin and the distal tubular reabsorption is known as facultative reabsorption of water and it is an active process. It also increases the permeability of the distal tubules of water. It causes the increased release of an enzyme known as hyaluronidase from the collecting tubules which is responsible for the increased passage of water through the tubules.
Hence, the correct answer is ‘A. Conservation of water’.

Note: Vasopressin also plays an important role in controlling the circadian rhythm which is the periods of sleepiness and wakefulness in a 24-hour cycle. It also helps in the maintenance of the internal temperature of the body. It is also associated with physiological and emotional activity.