Which one of the following hormones inhibits gastric secretion?

$A$ polypeptide secreted into the blood by the cells in the stomach wall,which stimulates the production of $HCl$ by the parietal cells of the stomach,is:

Contraction of the gallbladder is caused by:

$A -$ Secretin acts on the exocrine pancreas and stimulates the secretion of water and bicarbonate ions. $R -$ Cholecystokinin $(CCK)$ acts on both the pancreas and the gall bladder and stimulates the secretion of pancreatic enzymes and bile juice,respectively.

Inhibition of gastric secretion is brought about by

$CCK$ (Cholecystokinin) acts on which part of the digestive system?