Correct Answer: B

Rationale: Phospholipids are a major component of cell membranes, providing structural integrity and facilitating cell signaling. Cholesterol (choice A) is also present in cell membranes but in smaller amounts and plays a different role. Saturated (choice C) and triglyceride (choice D) are not major constituents of cell membranes.

Correct Answer: C

Rationale: Fluoride supplements should never be taken with milk because the fluoride binds with the calcium in the milk, thereby reducing the effectiveness of the fluoride supplement. Other beverages like water, juice, or soda do not share this characteristic as they do not contain the same level of calcium as milk. The rationale behind choosing milk as the correct answer is that it hampers the effectiveness of fluoride supplements, whereas the other choices do not.

Correct Answer: B

Rationale: A person with Celiac disease cannot consume Poptarts that contain gluten because gluten is a protein found in wheat, barley, and rye, triggering an autoimmune response in individuals with Celiac disease and damaging their small intestine. Even small quantities of gluten can lead to this harmful response, making choices 'A' and 'C' incorrect. While gluten-free Poptarts may be suitable for individuals with Celiac disease, regular Poptarts containing gluten are not safe for consumption by them, rendering choice 'D' incorrect as well.

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: C

Rationale: The correct answer is C: Carcinomas. Carcinomas are cancers that originate from epithelial tissues, which are the tissues lining the surfaces of organs and structures in the body. Leukemias (choice A) are cancers of the blood-forming cells, not epithelial tissues. Myelomas (choice B) are cancers that develop in plasma cells in the bone marrow, not epithelial tissues. Sarcomas (choice D) are cancers that arise from connective tissues like bone, cartilage, or muscle, not epithelial tissues. Therefore, choices A, B, and D are incorrect in the context of cancers originating from epithelial tissues.