Answer;
C) parathyroid glands; parathyroid hormone
Step-by-step explanation;
-Parathyroid glands (humans, four) are imbedded in the thyroid gland and they secrete the parathyroid hormone (PTH). So-called C cells dispersed throughout the thyroid gland, the parathyroids and thymus secrete another hormone, calcitonin. Both hormones play a significant role in the maintenance of calcium homeostasis.
-PTH, a polypeptide secreted in response to hypocalcemia raises the concentration of plasma calcium by; increasing renal calcium reabsorption, mobilizing calcium from bones by stimulating osteoclastic activity, in the presence of adequate amounts of vitamin D, stimulating the absorption of calcium from the small intestine; and lowering levels of plasma inorganic phosphate by inhibiting renal reabsorption of phosphate