Relating to carbohydrate digestion:

Correct Answer: B

Rationale: The correct answer is B because bile salts are essential for the digestion and absorption of fats, not carbohydrates. Cellulose cannot be digested by human amylases, making choice A incorrect. Starch digestion starts in the mouth with salivary amylase, not one-third in the mouth and two-thirds in the small gut, so choice C is incorrect. Carbohydrate digestion can occur simultaneously with protein digestion, so choice D is also incorrect. Bile salts aid in emulsifying fats, facilitating their digestion and absorption in the small intestine.

Correct Answer: D

Rationale: The correct answer is D, congenital pyloric stenosis. This condition typically presents in male infants around 3-6 weeks of age with projectile vomiting due to hypertrophy of the pyloric muscle, leading to obstruction at the pylorus. This causes the infant to forcefully vomit shortly after feeding. Meckel's diverticulum (A) presents with painless rectal bleeding. Esophageal atresia (B) presents with drooling and choking with feeding. Congenital diaphragmatic hernia (C) presents with respiratory distress and scaphoid abdomen due to herniation of abdominal organs into the chest cavity.

Correct Answer: B

Rationale: The correct answer is B: juvenile polyp. Juvenile polyps are benign growths commonly found in the colon and rectum of children. They have no significant tendency to undergo malignant transformation due to their non-neoplastic nature. They are typically small, solitary, and have a smooth surface. Familial polyposis (choice A) is a hereditary condition characterized by numerous polyps in the colon, which can progress to colorectal cancer. Villous adenomas (choice C) are precancerous lesions with a higher risk of malignant transformation. Carcinoid tumors (choice D) are neuroendocrine tumors that can be found in various parts of the body, including the gastrointestinal tract, and have the potential to be malignant.

Correct Answer: B

Rationale: The correct answer is B because HCl secretion is primarily carried out by parietal cells in the stomach lining. Parietal cells contain proton pumps that actively secrete HCl to aid in digestion. Chief cells secrete pepsinogen, not HCl (A is incorrect). Gastrin actually stimulates HCl secretion, so it doesn't inhibit it (C is incorrect). Acetylcholine (Ach) is a neurotransmitter that can stimulate, not inhibit, HCl secretion (D is incorrect). Therefore, option B is the correct choice based on the roles of parietal cells in HCl secretion.

Correct Answer: D

Rationale: The correct answer is D because none of the statements are true. A is incorrect because fat-soluble vitamins are incorporated into chylomicrons before absorption. B is incorrect because triglycerides are resynthesized in the intestinal cell but packaged into chylomicrons, not directly exported. C is incorrect because pancreatic lipase functions best at a pH of around 7-8, not 3. So, the correct answer is D as all the other choices are incorrect.