Answer: A. Hypothalamus
Explanation: Hypothalamus is part of the brain. It’s called “master switchboard” because it controls the endocrine system and releases hormone in the body. The hypothalamus controls the pituitary gland and other glands in the body.
Pituitary Gland is known as hypophysis cerebri. It’s call the “master gland” because it produces the hormones that stimulate the function of other endocrine glands.