What primarily determines the Dietary Reference Intake (DRI) for protein?

Correct Answer: D

Rationale: The Dietary Reference Intake (DRI) for protein is primarily determined by an individual's body weight. This is because the body's protein requirement is proportionate to its size, which is generally reflected in the body weight. Therefore, choice D is correct. Choices A, B, and C are incorrect: While factors such as fatty acid intake, gender, and height can influence an individual's overall nutritional needs, they do not directly determine the DRI for protein.

Correct Answer: A

Rationale: The correct answer is A: vitamin B12. Intrinsic factor is a glycoprotein produced by the stomach that is necessary for the absorption of vitamin B12 in the small intestine. Vitamin B12 binds to intrinsic factor in the stomach, forming a complex that is then absorbed in the ileum. This absorption process is crucial for preventing vitamin B12 deficiency. Choices B, C, and D are incorrect because they do not require intrinsic factor for absorption. Folate is absorbed in the small intestine through a different mechanism, niacin can be absorbed in the small intestine without the need for intrinsic factor, and vitamin B6 does not rely on intrinsic factor for absorption.

Correct Answer: D

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.

Correct Answer: C

Rationale: The correct answer is vitamin E. Vitamin E is the major antioxidant found in cell membranes, where it plays a crucial role in protecting them from oxidative damage. Although B12, beta-carotene, and vitamin A are important nutrients with specific functions in the body, they are not the primary antioxidants found in cell membranes. Vitamin E specifically localizes in cell membranes to neutralize free radicals and prevent lipid peroxidation, making it an essential antioxidant for cellular health.

Correct Answer: A

Rationale: Salmon is the correct answer as it is a rich source of omega-3 fatty acids, specifically EPA and DHA, which are known to be beneficial for heart health. Chicken, spinach, and eggs do not contain significant levels of omega-3 fatty acids compared to salmon. While eggs do contain some omega-3s, the amount is considerably lower than what is found in fatty fish like salmon.