What is the most common initial symptom of juvenile idiopathic arthritis?

Correct Answer: A

Rationale: The correct answer is A: Joint swelling and pain. These are the most common initial symptoms of juvenile idiopathic arthritis, typically affecting multiple joints. Skin rash (choice B), gastrointestinal bleeding (choice C), and neurological deficits (choice D) are not typical initial symptoms of juvenile idiopathic arthritis. Skin rash may be seen in other conditions like dermatitis or systemic lupus erythematosus, gastrointestinal bleeding may be associated with conditions like inflammatory bowel disease, and neurological deficits could be indicative of conditions like multiple sclerosis.

Correct Answer: B

Rationale: The correct answer is B. In a double-blind experiment, neither the subjects nor the researchers know which subjects are in the control or experimental group. This helps to eliminate bias and ensure that the results are more objective. Choice A is incorrect as in a double-blind experiment, subjects do not take turns receiving each treatment; it is about masking the treatment allocation. Choice C is incorrect because it implies that the researchers are aware of the group allocation, which goes against the principle of blinding in a double-blind study. Choice D is incorrect as both subject groups should not know whether they are in the control or experimental group to maintain the blindness of the study.

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.