Final answer:
An increase in acid from chyme leaving the stomach stimulates the secretion of secretin, which induces the pancreas to release bicarbonate solution to neutralize the chyme's acidity in the small intestine. Therefore, the correct option is A.
Step-by-step explanation:
An increase in acid from the chyme leaving the stomach stimulates an increase in the secretion of secretin. Secretin is a hormone released by the duodenum when acidic chyme from the stomach enters it. The primary function of secretin is to cause the pancreas to release a bicarbonate-rich solution into the small intestine to neutralize the acidity of chyme, facilitating the digestive process.
The gastric phase of digestion activates the release of several hormones and enzymes. However, when the pH drops too low, gastrin secretion is moderated to prevent excessive acid production and avoid heartburn. As the acidic chyme enters the duodenum, it triggers the secretion of secretin, which works with cholecystokinin (CCK) to initiate the release of additional digestive juices from the pancreas and bile from the gallbladder, ensuring proper digestion of nutrients.