Correct Answer: B

Rationale: The absorption of most nutrients occurs in the small intestine. This is where digested food is broken down further and absorbed into the bloodstream through the intestinal walls. The large intestine primarily absorbs water and electrolytes, while the stomach mainly aids in digestion by breaking down food with gastric juices. The mouth is responsible for the initial mechanical breakdown of food through chewing and the enzymatic action of saliva, but absorption does not occur there.

Correct Answer: A

Rationale: The correct answer is A: Villi. Villi are small fingerlike projections in the intestine that increase the surface area for nutrient absorption. Goblets (choice B) are mucus-secreting cells in the intestines. Lacteals (choice C) are lymphatic vessels in the small intestine that absorb dietary fats. Polyps (choice D) are abnormal tissue growths.

Correct Answer: A

Rationale: Ketones are produced when the body uses fat for energy due to the depletion of carbohydrate stores. When carbohydrate stores are depleted, the body turns to fat as its primary source of energy, leading to the production of ketones. Excess protein consumption does not directly lead to ketone production. Similarly, the depletion of protein stores or fat stores is not directly related to the production of ketones.

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: 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.