Which statement is true regarding the passage of food through the pyloric sphincter of the digestive tract? (i.e. the food has entered the stomach) At this time, bile has already been added. At this time, proteins are completely digested. At this time, the mixture of food is acidic. none of the above

The correct answer is: **At this time, the mixture of food is acidic.**<br /><br />Here's why:<br /><br />* **Pyloric Sphincter:** This sphincter controls the passage of chyme (partially digested food) from the stomach into the duodenum (the first part of the small intestine).<br /><br />* **Stomach Acid:** The stomach secretes hydrochloric acid (HCl), creating a highly acidic environment. This acidity helps to denature proteins, activate pepsin (a protein-digesting enzyme), and kill harmful bacteria. Food entering the small intestine via the pyloric sphincter is therefore acidic.<br /><br />* **Bile and Protein Digestion:** Bile, which aids in fat digestion, and the completion of protein digestion both occur *after* the pyloric sphincter, in the small intestine. Bile is released into the duodenum from the gallbladder. Protein digestion begins in the stomach but continues and is completed in the small intestine.<br />