A and B secrete their hormones when they receive orders from gland C .
Which of the following can A, B and C respectively be ?

The correct answer is Thyroid, Adrenal glands, Pituitary.

1. Understanding the Role of Gland C (Pituitary Gland):
The pituitary gland is known as the "master gland" of the endocrine system. It secretes tropic hormones that stimulate and regulate the activity of other endocrine glands, instructing them to produce and release their respective hormones.

2. Identifying Glands A and B:
Glands A and B are endocrine glands whose hormone secretion is directly controlled by signals/hormones from the pituitary gland (gland C):

• Thyroid Gland (A): Secretes thyroxine under the stimulation of Thyroid-Stimulating Hormone (TSH) released by the pituitary gland.
• Adrenal Glands (B): The adrenal cortex secretes cortisol and other corticosteroids when stimulated by Adrenocorticotropic Hormone (ACTH) released by the pituitary gland.

3. Evaluating the Given Options:
• Option 1: Pancreas, Adrenal glands, Thyroid — Incorrect (Pancreas insulin/glucagon secretion is regulated mainly by blood glucose levels, not pituitary signals).
• Option 2: Thyroid, Adrenal glands, Pituitary — Correct (Thyroid and Adrenal glands release hormones upon receiving signals from the Pituitary gland).
• Option 3: Testes, Ovaries, Thyroid — Incorrect (Thyroid is not the master gland for gonadotropin signaling in this context).
• Option 4: Pituitary, Pancreas, Thyroid — Incorrect (Pituitary is gland C, not A).

Therefore, A, B, and C respectively are Thyroid, Adrenal glands, and Pituitary.