Correct option: BExplanation:The source of somatostatin is same as that of insulin and glucagon. Somatostatin is produced by the delta cells of the islets of Langerhans in pancreas. It blocks the secretion of insulin and glucagon from adjacent beta and alpha cells and have the same source of secretion as them.Thyroxine and calcitonin are produced by thyroid gland. Whereas, somatotropin or growth hormone, prolactin, vasopressin and oxytocin are produced by pituitary glands. These hormones are not produced by pancreas and have different sources not same as somatostatin.Thus, Option B is correct.