Correct Answer: A

Rationale: Glucose serves as a primary source of energy for the body, especially for the brain and muscles. Choice B is incorrect because glucose itself is not responsible for transporting oxygen to cells. Choice C is incorrect as glucose is converted to glycogen, not the other way around. Choice D is incorrect as glucose itself does not play a direct role in maintaining body weight.

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.

Correct Answer: C

Rationale: The correct answer is C: 'presence of food in the stomach.' Gastric secretions are stimulated when food enters the stomach, triggering nerve and hormonal responses. This process prepares the stomach for digestion. Choices A, B, and D are incorrect because ingesting water, swallowing reflex, and the closing of the pyloric sphincter do not directly stimulate the release of gastric secretions.

Correct Answer: C

Rationale: The correct answer is C: pancreas. Secretin stimulates the pancreas to release bicarbonate, which acts as a buffering solution to neutralize the acid entering the duodenum from the stomach. This process helps in maintaining the pH balance in the small intestine. Choice A, stomach, is incorrect as the stomach does not produce the buffering solution needed for the duodenum. Choice B, liver, is incorrect because secretin does not directly stimulate the liver to produce a buffering solution. Choice D, oxyntic cells, is also incorrect as these cells in the stomach are responsible for producing gastric acid, not the buffering solution needed in the duodenum.

Correct Answer: B

Rationale: The correct answer is B: nonessential amino acids. Nonessential amino acids can be synthesized by the body, so they do not need to be obtained through the diet. Essential amino acids, choice A, must be obtained from the diet because the body cannot produce them. Choices C and D, complete and incomplete amino acids respectively, do not accurately describe the classification of amino acids based on synthesis by the body.