The gland which regulates the level of calcium in the blood is

Options

A. Thyroid
B. Adrenal
C. Parathyroids
D. Pituitary

Explanation

**Step-by-Step Solution:**

1. **Identify the Gland Involved**: The question asks for the gland that regulates calcium levels in the blood. The key gland responsible for this function is the parathyroid gland.

2. **Understand the Function of the Parathyroid Gland**: The parathyroid gland secretes a hormone called parathormone (PTH). This hormone plays a crucial role in regulating calcium levels in the blood.

3. **Target Organs of Parathormone**: The target organs for parathormone are the bones and the small intestine. Parathormone increases calcium levels in the blood by promoting the release of calcium from bones and enhancing calcium absorption from the small intestine.

4. **Role of the Thyroid Gland**: The thyroid gland acts as an antagonist to the parathyroid gland. While the parathyroid gland increases calcium levels in the blood, the thyroid gland helps lower these levels by promoting the deposition of calcium into the bones.

5. **Conclusion**: Based on the functions of these glands, the correct answer to the question is the parathyroid gland, as it is the primary gland responsible for regulating calcium levels in the blood.

**Final Answer**: The gland which regulates the level of calcium in the blood is the parathyroid gland.

---