The lining of the stomach and intestine is protected from self-digestion by:

Correct Answer: C

Rationale: The correct answer is C: mucus. Mucus forms a protective barrier that prevents the stomach and intestine from digesting themselves. Pepsinogen (choice A) is an inactive form of pepsin, a digestive enzyme, and does not protect the stomach lining. Bile (choice B) aids in the digestion and absorption of fats but does not protect the stomach lining. Fat (choice D) is a nutrient and energy source; it does not play a role in protecting the stomach and intestine from self-digestion.

Correct Answer: A

Rationale: The correct answer is A: Smelling or seeing food. When an individual smells or sees food, it can trigger the body to start producing digestive secretions in anticipation of food consumption. This physiological response helps prepare the digestive system for the incoming meal. Choices B, C, and D are incorrect because grocery shopping, fasting, and exercise do not directly stimulate digestive secretions in the same way that the sight or smell of food does.

Correct Answer: D

Rationale: The correct answer is D, amylase. Amylase is an enzyme produced by the salivary glands that initiates the digestion of carbohydrates in the mouth. Pepsin (choice A) is produced in the stomach to digest proteins, trypsin (choice B) is produced in the pancreas to digest proteins, and sucrase (choice C) is produced in the small intestine to break down sucrose. Therefore, choices A, B, and C are incorrect in the context of an enzyme secreted by the salivary glands.

Correct Answer: A

Rationale: The parotid, submandibular, and sublingual glands are the main salivary glands located in the mouth. They play a crucial role in producing saliva, which aids in digestion. The stomach (choice B) is where gastric juices are produced, the pancreas (choice C) secretes digestive enzymes into the small intestine, and the duodenum (choice D) is the first part of the small intestine where most chemical digestion occurs. Therefore, the correct answer is the mouth (choice A) as it is where these salivary glands are situated.

Correct Answer: D

Rationale: The correct answer is D: gastroesophageal reflux disease (GERD). GERD occurs when stomach acid flows back into the esophagus, causing symptoms like heartburn and regurgitation. Choice A, hiatal hernia, is a condition where part of the stomach pushes up into the chest through an opening in the diaphragm. Choice B, diverticulitis, is inflammation or infection of small pouches that can form in the lining of the digestive system. Choice C, gastroenteritis, is inflammation of the stomach and intestines typically caused by a viral or bacterial infection. Therefore, only choice D accurately describes the regurgitation or reflux of acidic stomach contents back into the esophagus.