Explanation:

- Option 1: Thymus

- The thymus gland is situated in the chest, between the lungs. It's part of the lymphatic system and plays a key role in developing the body's immune system, particularly during early life.

- Option 2: Pituitary

- The pituitary gland is located at the base of the brain. It’s known as the “master gland” because it controls various other hormone glands in the body.

- Option 3: Hypothalamus

- The hypothalamus is also in the brain, situated below the thalamus. It links the nervous system to the endocrine system via the pituitary gland.

- Option 4: Pineal

- The pineal gland is located in the brain, near the center, and it secretes the hormone melatonin, which regulates sleep-wake cycles.