Correct Answer: A

Rationale: The correct answer is iron. Iron is essential for enzyme function and energy production within the mitochondria. While cobalt is important for certain enzymes, it is not the primary mineral involved in this specific function. Hemoglobin is a protein in red blood cells that carries oxygen, not a mineral involved in enzyme actions. Vitamin B12 is crucial for nerve function and DNA synthesis but is not directly related to controlling enzyme actions in mitochondria.

Correct Answer: D

Rationale: The correct answer is D: 45% to 65%. Carbohydrates should contribute between 45% to 65% of the total daily caloric intake for healthy individuals to maintain a balanced diet. Choices A, B, and C are incorrect because they suggest lower ranges, which may not provide sufficient energy from carbohydrates for overall health and well-being.

Correct Answer: C

Rationale: Low income is a significant factor contributing to marginal nutritional status due to limited access to nutritious food. While dependence on caffeine or acute illness can impact health, they are not as directly linked to marginal nutrition as low income. The size of the family unit may affect food distribution within the household but is not as directly related to marginal nutritional status as low income.

Correct Answer: C

Rationale: The correct answer is C: Healthy People 2020. Healthy People 2020 is a government initiative that sets goals for improving the health of Americans, including specific nutritional objectives. Choices A, B, and D are not examples of government nutrition policies. MyPlate Food Guidance System is a visual tool to help individuals make healthy food choices, Dietary Guidelines for Americans 2010 provide evidence-based advice for Americans two years and older, and Dietary Reference Intakes (DRIs) are a set of nutrient reference values.

Correct Answer: A

Rationale: The correct answer is A: prevention and control of chronic diseases. In this century, nutritional recommendations have increasingly emphasized the importance of preventing and managing chronic diseases like obesity, diabetes, cardiovascular diseases, and cancer. Lifestyle factors such as diet play a significant role in the development of these conditions. Option B, improved sanitation and public health, although important for overall health, is not the primary focus of nutritional recommendations. Option C, prevention and control of infectious diseases, is also crucial but does not reflect the current major focus of nutritional recommendations. Option D, development of healthful foods using food technology, is a valid area of interest but is not the primary shift in focus observed in nutritional recommendations.