You have been asked to help a top nutrition researcher conduct human experiments on vitamin C. As the subjects walk into the laboratory, you distribute all the vitamin C pill bottles to the girls and all the placebo pill bottles to the boys. What should you have done?

Correct Answer: D

Rationale: The correct approach in a scientific experiment is to prevent yourself from knowing the contents of the pill bottles and distribute them randomly to the subjects. This randomization helps to avoid bias and ensures that the results are not influenced by preconceived notions. Option A is incorrect because it introduces gender bias by assigning pills based on gender. Option B is incorrect as it mentions telling the subjects what they are getting, which could lead to placebo effects. Option C is incorrect as it suggests disclosing group information to the subjects, which can also introduce bias.

Correct Answer: A

Rationale: The correct answer is A. Vitamins are organic compounds, containing carbon, which is a key characteristic that differentiates them from minerals. Choice B is incorrect because vitamins do not provide energy; they are not a source of calories. Choice C is incorrect as both vitamins and minerals are considered micronutrients due to being essential in small amounts. Choice D is incorrect because while it is true that vitamins are needed in small amounts, this is not the characteristic that sets them apart from minerals.

Correct Answer: B

Rationale: Randomization is crucial in a scientific experiment to eliminate bias in the assignment of subjects to groups. By randomly assigning subjects, it helps ensure that any differences observed in the outcomes are due to the experimental treatment and not to preexisting differences between groups. Choice A is incorrect because randomization does not guarantee representativeness but rather minimizes the impact of confounding variables. Choice C is not entirely accurate; while randomization can contribute to accuracy and validity, its primary purpose is to reduce bias. Choice D is incorrect as the goal of randomization is not to balance the number of subjects but to prevent systematic differences between groups.

Correct Answer: C

Rationale: Peer review is crucial in scientific research to verify the accuracy and validity of research findings. By subjecting research papers to evaluation by experts in the field, peer review ensures that the study's methods, results, and conclusions are robust and reliable. This process helps to maintain high standards of quality in scientific publications, providing credibility to the research. Choices A and D are incorrect because the primary purpose of peer review is not to expedite publication or solely enhance credibility; its core function is to validate the research's accuracy and validity. Choice B, while beneficial, is not the primary reason for peer review; replication is a byproduct of the rigorous evaluation of research methods and findings.

Correct Answer: C

Rationale: The correct answer is C. An essential nutrient is a substance that is necessary for normal body functioning but cannot be synthesized in adequate amounts by the body, therefore it must be obtained from the diet. Choices A, B, and D are incorrect because essential nutrients are not synthesized by the body, they are necessary for body functioning, and they are not typically stored in the body for long periods.