Correct Option: A  [ brain ]
Remark:
Explanation: The pituitary gland is a small, pea-sized endocrine gland located at the base of the brain, just beneath the hypothalamus. It is often called the "master gland" because it secretes several hormones (like growth hormone, TSH, FSH, LH, and prolactin) that control other endocrine glands and various physiological processes.