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: A

Rationale: The correct answer is the amino group. Amino groups are functional groups found in amino acids, which are the building blocks of proteins. These groups contain nitrogen and are essential for the structure and function of proteins. The carboxyl group (choice B) contains carbon, oxygen, and hydrogen, while the peptide bond (choice C) is a covalent bond formed between amino acids in a protein chain. The side chain (choice D) refers to the unique chemical structure attached to the central carbon of an amino acid and varies among different amino acids, but it does not specifically contain nitrogen.

Correct Answer: A

Rationale: Bacteria found in the colon are important because they synthesize important vitamins, such as vitamin K. This aids in the body's overall health and functioning. Choice B is incorrect because absorption primarily occurs in the small intestine, not the colon. Choice C is incorrect as the synthesis of minerals is not a primary function of colon bacteria. Choice D is incorrect as the digestion process mainly occurs in the stomach and small intestine.

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: C

Rationale: The correct answer is C - intramural nerve plexus. This network of nerves regulates the muscular movements within the gastrointestinal wall. The gastric nerve plexus (choice A) specifically relates to the stomach, not the entire gastrointestinal tract. The biliary nerve plexus (choice B) is associated with the bile ducts and gallbladder, not the regulation of muscular action. The intestinal nerve plexus (choice D) is a general term that doesn't specifically refer to the network of nerves within the gastrointestinal wall.