Correct Answer: C

Rationale: The correct answer is C. Understanding serving sizes is crucial because most people have difficulty estimating the amount of food they eat. It helps individuals accurately track their intake, which is essential for maintaining a healthy diet and avoiding overeating. Choice A is incorrect because the question focuses on portion sizes rather than specific nutrients. Choice B is incorrect as it presents an unsupported claim about serving sizes decreasing. Choice D is incorrect as weighing food portions is not always necessary to check serving sizes; understanding standard serving sizes allows for a more practical approach to portion control.

Correct Answer: C

Rationale: Dietary guidelines are designed to assist individuals in making smart food choices by providing recommendations on what to eat to maintain good health. While portion sizes may be a part of these guidelines, they are not the primary focus. Designing a personal food plan involves individual preferences and needs, which may go beyond general guidelines. Avoiding excessive nutrient intakes is important, but dietary guidelines aim to provide balanced recommendations rather than just focusing on avoiding excess.

Correct Answer: C

Rationale: The primary function of carbohydrates as a food source is to supply energy. Carbohydrates are the body's main source of energy, providing fuel for various physiological functions. Choice A is incorrect because carbohydrates do not primarily regulate metabolic processes; that role is mainly attributed to enzymes and hormones. Choice B is incorrect because proteins are primarily responsible for building body tissue. Choice D is incorrect because fiber, not all carbohydrates, provides bulk in the diet.

Correct Answer: A

Rationale: The correct answer is A: potassium and vitamin A. Vegetables are an excellent source of potassium and vitamin A, both essential for maintaining overall health. Iron and vitamin C (choice B) are commonly found in foods from the Protein and Fruits groups, respectively. Calcium and vitamin B12 (choice C) are more abundant in dairy products and animal-based foods. Sodium and vitamin E (choice D) are not the major nutrients typically supplied by vegetables.

Correct Answer: B

Rationale: The correct answer is B: 120. Carbohydrates provide 4 kcal per gram, so 30 grams of carbohydrates will provide 120 kcal. This is calculated by multiplying the grams of carbohydrate (30) by the kcal per gram (4). Choices A, C, and D are incorrect because they do not reflect the correct calculation based on the energy content of carbohydrates.