Questions: The produces that increases blood levels of sodium and water and decreases blood levels of potassium. - adrenal medulla; aldosterone - thyroid gland; thyroxine - hypothalamus; antidiuretic hormone - adrenal cortex; aldosterone - parathyroid; parathyroid hormone

The answer is the fourth one (D): adrenal cortex; aldosterone.

Explanation for each option:

1. Adrenal medulla; aldosterone: This is incorrect. The adrenal medulla produces catecholamines, such as adrenaline (epinephrine) and noradrenaline (norepinephrine), not aldosterone.

2. Thyroid gland; thyroxine: This is incorrect. The thyroid gland produces thyroxine (T4) and triiodothyronine (T3), which are involved in regulating metabolism, not in regulating blood levels of sodium, water, or potassium.

3. Hypothalamus; antidiuretic hormone: This is incorrect. The hypothalamus produces antidiuretic hormone (ADH), which helps regulate water balance in the body by increasing water reabsorption in the kidneys, but it does not directly affect sodium or potassium levels.

4. Adrenal cortex; aldosterone: This is correct. The adrenal cortex produces aldosterone, a hormone that increases the reabsorption of sodium and water in the kidneys and promotes the excretion of potassium, thereby increasing blood levels of sodium and water and decreasing blood levels of potassium.

5. Parathyroid; parathyroid hormone: This is incorrect. The parathyroid glands produce parathyroid hormone (PTH), which regulates calcium levels in the blood, not sodium, water, or potassium levels.

Summary: The adrenal cortex produces aldosterone, which increases blood levels of sodium and water and decreases blood levels of potassium.