Correct Answer: B

Rationale: The correct answer is B: Carbohydrates and fats. Carbohydrates are the body's primary and most efficient source of energy, providing fuel for daily activities. Fats are also a significant energy source, especially during times of prolonged or intense exercise. Proteins are primarily used for building and repairing tissues, not as a major energy source. Vitamins and minerals are essential for various bodily functions but do not serve as direct sources of energy.

Correct Answer: C

Rationale: The correct answer is C: mucus. Mucus forms a protective barrier that prevents the stomach and intestine from digesting themselves. Pepsinogen (choice A) is an inactive form of pepsin, a digestive enzyme, and does not protect the stomach lining. Bile (choice B) aids in the digestion and absorption of fats but does not protect the stomach lining. Fat (choice D) is a nutrient and energy source; it does not play a role in protecting the stomach and intestine from self-digestion.

Correct Answer: C

Rationale: Gluconeogenesis mainly occurs in the liver. It is a process where glucose is synthesized from non-carbohydrate sources such as amino acids and glycerol. The liver is the primary site for gluconeogenesis due to the presence of key enzymes and substrates required for this process. Muscles do not play a significant role in gluconeogenesis, making choice A incorrect. The pancreas is involved in the regulation of blood sugar levels through insulin and glucagon but is not the primary site for gluconeogenesis, so choice B is incorrect. The spleen is not a major organ involved in glucose metabolism, making choice D incorrect.

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: ileocecal valve. The ileocecal valve is located between the small intestine and the cecum, controlling the passage of chyme. The pyloric valve (choice B) is located between the stomach and the small intestine, regulating the passage of food from the stomach to the small intestine. The cardiac valve (choice C) refers to the valve between the esophagus and the stomach. The hepatic valve (choice D) is not a correct term related to the passage of chyme from the small intestine into the cecum.