Correct Answer: B

Rationale: The most common type of kidney stone is calcium-based, specifically calcium oxalate. This is usually due to high calcium levels in the urine, which can be caused by dietary factors or certain metabolic disorders. Cystine stones, on the other hand, are less common and occur in individuals with a hereditary disorder leading to excessive excretion of certain amino acids. Struvite stones are often formed in response to an infection. Uric acid stones may occur in individuals who do not consume sufficient fluids or who lose too much fluid, among other factors. Therefore, while all these substances can form stones in the kidneys, calcium stones are the most common.

Correct Answer: B

Rationale: Pepsin, choice B, is the correct answer as it is a proteolytic enzyme that is essential for the breakdown of large protein molecules in the stomach. Gastric lipase, choice A, is incorrect because it primarily targets fats, not proteins, hence it is not involved in protein hydrolysis. Mucus, choice C, is incorrect as it serves to protect the stomach lining from acidic gastric juices and does not play a direct role in protein digestion. Intrinsic factor, choice D, is incorrect as it is vital for the absorption of Vitamin B12 in the small intestine and doesn't participate in the process of hydrolyzing proteins.

Correct Answer: D

Rationale: The correct answer is D: potato chips. Potato chips, especially when fried in hydrogenated oils, are a common source of trans fats, which are linked to an increased risk of coronary heart disease (CHD). Hot dogs (choice A) can also contain trans fats if made with processed meats and added fats. Whole milk (choice B) and fatty fish (choice C) do not typically contain trans fats, making them less likely sources compared to potato chips.

Correct Answer: C

Rationale: Damage to the stomach can lead to a reduced ability to produce gastric acid (Choice C) and intrinsic factor, the latter of which is crucial for vitamin B12 absorption (Choice D). That's why these two choices are correct. The stomach doesn't play a direct role in the digestion of carbohydrates (Choice A) as this process primarily occurs in the small intestine with the help of pancreatic enzymes. Similarly, bile is produced by the liver and stored in the gallbladder, not the stomach, hence stomach damage wouldn't lead to an inability to produce or secrete bile (Choice B).

Correct Answer: C

Rationale: The placenta plays a crucial role in producing hormones that are necessary for maintaining pregnancy, supporting fetal development, and preparing the mother's body for childbirth. Choices A, B, and D are incorrect because the placenta's primary function is not to surround and cushion the fetus, combine blood stores for nutrient exchange, or absorb vitamins and minerals. While the placenta does facilitate the exchange of nutrients and oxygen between the mother and fetus, its hormone production is the most critical function during pregnancy.