Final answer:
Somatostatin, produced by the delta cells of the pancreas, inhibits the secretion of both glucagon and insulin. It does not stimulate the secretion of insulin, thus making option 'C' the incorrect statement.
Step-by-step explanation:
The hormone somatostatin has several roles within the body, particularly in regulating other hormones. It is true that it is produced by the delta cells of the pancreas, and it does indeed inhibit the secretion of glucagon. However, contrary to one of the options given, somatostatin actually inhibits the secretion of insulin, not stimulates it. Therefore, 'C. It stimulates the secretion of insulin' is not true of somatostatin.
The correct statement about somatostatin is that it inhibits the release of both glucagon and insulin, helping regulate blood glucose levels. This hormone also inhibits the production of growth hormone by the pituitary gland, among other functions.