Which of the following causes an increase in sodium reabsorption in distal convoluted tubules?
A) Increase in aldosterone levels
B) Decrease in antidiuretic hormone levels
C) Decrease in aldosterone levels
D) None of the above

Hint: The nephron is the structural and function unit of the kidney thus the excretory system. Nephron is made up of Bowman’s capsule, proximal convoluted tubule, Henle’s loop, distal convoluted tubule and collecting duct. Reabsorption takes in three regions – proximal convoluted tubule, Henle’s loop, distal convoluted tubule.

Complete answer:
Aldosterone is secreted from the adrenal cortex.
The main function of aldosterone is to serve as a stimulant of the renal absorption of sodium ions and water. This leads to the increment of the blood volume.
When the aldosterone level is reduced, it helps to increase the sodium secretion by Distal Convoluted Tubules.
The adrenal glands are endocrine glands that contain various hormones including adrenaline, aldosterone and cortisol steroids. The glands are also called adrenal glands. They're over the kidneys. Each gland has an external cortex that creates steroid and internal medulla hormones. The cortex is split into three areas: the glomerulus zone, the fasciculate area and the reticular zone. Triplicates of steroid hormones are formed by the adrenal cortex, which is the mineralocorticoids.

Hence, the correct answer is option A. Increase in aldosterone levels.

Note:
Antidiuretic hormone or ADH is secreted by posterior pituitary gland that targets the nephron to increase the water reabsorption in the proximal convoluted tubule, Henle’s loop, distal convoluted tubule and collecting duct which thereby decreases the water content in urine. The renin – angiotensin – aldosterone system plays a major role in water and sodium reabsorption by the nephron.