Correct Answer: A

Rationale: Cholecystokinin (CCK) is produced in the duodenum, not the stomach, pancreas, or liver. It is released in response to the presence of food in the duodenum, where it plays a crucial role in regulating digestive processes by stimulating the release of bile from the gallbladder and enzymes from the pancreas. Therefore, the correct answer is the duodenum (Choice A). Choices B, C, and D are incorrect because CCK is not produced in the stomach, pancreas, or liver.

Correct Answer: A

Rationale: The correct answer is A: kwashiorkor. Kwashiorkor is a form of protein-energy malnutrition that arises due to a protein-deficient diet. This condition leads to symptoms such as edema, skin lesions, and fatty liver. Choice B, marasmus, is a form of PEM caused by overall malnutrition (protein and calorie deficiency), resulting in severe wasting and muscle loss. Choice C, anemia, is a condition characterized by a deficiency of red blood cells or hemoglobin, not specifically related to protein deficiency. Choice D, beriberi, is a disease caused by thiamine (Vitamin B1) deficiency, not a form of PEM related to protein deficiency.

Correct Answer: D

Rationale: Eggs are considered a source of complete protein because they contain all the essential amino acids required by the body. The other options, cereal grains, beans, and nuts, do not provide all the essential amino acids in the necessary proportions to be classified as complete proteins.

Correct Answer: A

Rationale: The correct answer is A: 1.8 and 3.5. Pepsin, an enzyme involved in protein digestion, functions optimally in an acidic environment, specifically between pH 1.8 and 3.5. This low pH is necessary for pepsin to break down proteins effectively. Choices B, C, and D are incorrect because pepsin requires a highly acidic environment, ruling out the pH ranges listed in those options.

Correct Answer: D

Rationale: The correct answer is D: portal blood system. After absorption, carbohydrates and proteins are transported via the portal blood system to the liver for further processing and distribution to the rest of the body. Choices A, B, and C are incorrect. Enterohepatic circulation refers to the recycling of compounds between the liver and the intestines, not the direct route for absorbed nutrients. Gastrointestinal circulation is a vague and non-specific term, not specifically related to the transport of absorbed nutrients. The common bile duct is involved in transporting bile from the liver and gallbladder to the small intestine, not the end products of carbohydrate and protein digestion.