The correct answer is Option D: Vasopressin from Neurohypophysis. Here's why:

Diuresis refers to increased urine production. Let's break down how each option affects urine production:

Option A: Renin from JG cells via switching off the osmoreceptors

Renin, released from the juxtaglomerular (JG) cells, is part of the renin-angiotensin-aldosterone system (RAAS). RAAS primarily affects blood pressure and volume by:

• Increasing sodium reabsorption: This leads to water retention, thus increasing blood volume.
• Constricting blood vessels: This raises blood pressure.

While RAAS can indirectly influence urine production, it doesn't directly prevent diuresis. Also, osmoreceptors are stimulated by increased blood osmolarity, not switched off by renin.

Option B: ANF from atria of the heart

Atrial natriuretic factor (ANF) is a hormone released from the heart's atria in response to high blood pressure. ANF acts to:

• Decrease sodium reabsorption: This leads to increased urine output (diuresis) and lowers blood volume.
• Dilate blood vessels: This lowers blood pressure.

Therefore, ANF actually promotes diuresis, not prevents it.

Option C: Aldosterone from adrenal medulla

Aldosterone is a hormone secreted by the adrenal cortex, not the medulla. Its primary function is to increase sodium reabsorption in the kidneys, leading to water retention and increased blood volume. This effect is opposite to diuresis.

Option D: Vasopressin from Neurohypophysis

Vasopressin, also known as antidiuretic hormone (ADH), is released from the posterior pituitary gland (neurohypophysis). Vasopressin plays a crucial role in regulating water balance by:

• Increasing water reabsorption in the kidneys: This leads to concentrated urine and decreased urine output, preventing diuresis.

Vasopressin's action is the direct opposite of diuresis, making it the most effective in preventing excessive urine production.

In summary: Vasopressin (ADH) is the primary hormone responsible for preventing diuresis by increasing water reabsorption in the kidneys.