Correct Answer: C

Rationale: The side chain, also known as the R group, is what differentiates one amino acid from another. It imparts unique properties to each amino acid, thereby influencing their roles and functions in proteins. The amine group (Choice A) and the acid group (Choice B) are components of all amino acids and do not cause the differences among various amino acids. Choice D is incorrect as it suggests that none of the given options account for the differences, which is not true as the side chain does.

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: C

Rationale: The best way to ensure adequate nutrition for a stroke patient who frequently chokes and coughs when eating and has difficulty feeding herself is to provide tube feedings. Tube feedings are a safe and effective method to deliver nutrition directly to the stomach or intestines, bypassing the swallowing mechanism, reducing the risk of aspiration. Having an aide feed her each meal (choice A) may not address the underlying issue of swallowing difficulty and aspiration risk. Asking a family member to be present at each meal (choice B) does not provide a definitive solution to the patient's nutritional needs. Placing the patient on total parenteral nutrition (TPN) (choice D) is a more invasive and typically reserved for patients who cannot tolerate enteral feedings or have non-functional gastrointestinal tracts.

Correct Answer: D

Rationale: The correct answer is D, 'Limiting saturated fat intake to less than 7% of energy intake.' This is a central feature of the therapeutic lifestyle changes (TLC) recommended for treating high blood cholesterol. Saturated fats can increase low-density lipoprotein (LDL) cholesterol, a significant risk factor for heart disease. Choice A is incorrect because while it is recommended to limit cholesterol intake, it's not suggested to avoid all foods containing cholesterol entirely in the TLC. Choice B is also incorrect as although reducing sodium intake is beneficial for controlling blood pressure, it's not specifically targeted in the TLC for managing high cholesterol. Lastly, while limiting total fat intake is a healthy guideline, it's not as specific or effective as limiting saturated fat intake, making choice C also incorrect.

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.