Which nutrient source yields more than 4 kcalories per gram?

Correct Answer: A

Rationale: The correct answer is plant fats (Choice A). Fats, including plant fats, provide 9 kcalories per gram, which is more than 4 kcalories. Plant proteins (Choice B) and animal proteins (Choice C) provide 4 kcalories per gram. Plant carbohydrates (Choice D) also provide 4 kcalories per gram. Therefore, Choices B, C, and D are incorrect because they do not yield more than 4 kcalories per gram.

Correct Answer: A

Rationale: The correct answer is A. Energy is released during the metabolism of energy nutrients. This released energy is utilized by the body for various functions. Choice B is incorrect because the metabolism of energy nutrients does not directly result in an increase in body fat. Choice C is incorrect as energy is not destroyed but rather transformed and utilized by the body. Choice D is incorrect as the metabolism of energy nutrients does not lead to a decrease in body water.

Correct Answer: C

Rationale: When an increase in exercise is accompanied by a decrease in body weight, it demonstrates a negative correlation. This means that as one variable (exercise) increases, the other variable (body weight) decreases. Choice A, 'variable effect,' is vague and does not accurately describe the relationship between exercise and body weight. Choice B, 'positive correlation,' is incorrect because in a positive correlation, both variables would increase or decrease together. Choice D, 'randomization effect,' is unrelated to the scenario described.

Correct Answer: D

Rationale: The Recommended Dietary Allowances (RDAs) are the best measure to describe the amounts of nutrients that should be consumed by the population. RDAs represent the average daily intake level that meets the nutrient requirements of nearly all (97-98%) healthy individuals in a particular life stage and gender group. Choice A, the Dietary Reference Intakes, provide a set of nutrient intake values but do not specifically address the average daily amount of a nutrient considered adequate for practically all individuals. Choice B, the Tolerable Upper Intake levels, focus on the maximum daily amount of a nutrient deemed safe for most healthy people, not the average daily amount needed. Choice C, the Estimated Average Requirements, reflect the average daily amount of a nutrient needed by half of the healthy individuals, which is not as comprehensive as the RDAs that cater to nearly all healthy people.

Correct Answer: D

Rationale: The correct answer is D. A placebo serves as a control for comparison with the treatment group, helping to eliminate bias and ensure the results are due to the treatment itself. Placebos are crucial in research to distinguish the actual effect of the treatment from psychological or subjective factors. Choice A is incorrect because the purpose of a placebo is not related to reducing the cost of the experiment. Choice B is incorrect because while placebos are used in double-blind studies, their primary purpose is not to make the experiment double-blind. Choice C is incorrect because the purpose of a placebo is not to increase the number of participants but rather to serve as a comparison group for the treatment being tested.