Correct Answer: B

Rationale: Cariogenic foods and beverages lower the pH level in the mouth to below 5.5. This is a critical threshold, as it is the point at which enamel begins to demineralize, increasing the risk of dental caries. Therefore, options 'A', 'C', and 'D' are incorrect. Although a pH level of 5, as suggested by option 'A', would indeed lead to demineralization, it's not the threshold value. The pH levels suggested by options 'C' and 'D' (6 and 6.5, respectively) are higher than the critical value of 5.5, which means they would not initiate enamel demineralization and the subsequent risk of dental caries.

Correct Answer: A

Rationale: In patients with stage 5 chronic kidney disease (CKD), also known as end-stage renal disease, the kidney function is significantly compromised. This severe condition is characterized by a glomerular filtration rate (GFR) of less than 15 mL/min/1.73 m², as correctly stated in choice A. Choices B, C, and D suggest higher GFR values, which are not indicative of stage 5 CKD. Specifically, a GFR of less than 30 mL/min/1.73 m² indicates stage 4 CKD, less than 90 mL/min/1.73 m² signifies stage 3 CKD, and a typical healthy individual usually has a GFR of around 125 mL/min/1.73 m², which is far above the GFR for stage 5 CKD.

Correct Answer: C

Rationale: Calcium is the most important nutrient for bone health and the prevention of osteoporosis. Calcium plays a crucial role in maintaining bone density and strength. Vitamin A is important for vision and immune function but is not directly related to bone health. Iron is essential for oxygen transport in the blood, while protein is important for muscle growth and repair. However, in the context of preventing osteoporosis, calcium is the key nutrient.

Correct Answer: D

Rationale: The correct answer is 'D. triglyceride.' Triglycerides are composed of one glycerol molecule and three fatty acids, making them the primary form of stored fat in the body. Cholesterol (A) is a different type of lipid, phospholipids (B) have two fatty acids, and 'saturated' (C) refers to the structure of fatty acids, not a specific lipid containing 3 fatty acids.

Correct Answer: A

Rationale: Buying a few pieces of fresh fruit at different stages of ripeness ensures that Lynn will have ripe fruit available over several days, reducing waste and cost. Choice B focuses on frozen vegetables but doesn't address the variety and ripeness factor like Choice A. Choice C is about cheese, which may not be as essential for a nutritious diet compared to fresh fruit. Choice D suggests avoiding certain foods in bulk, which might not be as relevant for maintaining a nutritious diet economically as the strategy in Choice A.