Answer:
B. pituitary gland
Step-by-step explanation:
The pituitary gland releases the antidiuretic hormone (ADH), vasopressin. ADH plays a crucial role in regulating the body's water balance and controlling urine production. However, it does not directly regulate calcium levels in the bloodstream.
The parathyroid glands, located near the thyroid gland, are responsible for regulating calcium levels in the bloodstream. They release parathyroid hormone (PTH), which helps increase calcium levels when too low.
Therefore, the correct gland responsible for regulating calcium levels in the bloodstream is the parathyroid gland, not the pituitary gland.