Which of these body parts does not contain melanin?

Correct Answer: D

Rationale: The iris is the colored part of the eye that determines the eye's color. Melanin is not present in the iris, unlike hair, nails, and skin. Melanin gives color to hair, nails, and skin, but not to the iris. Therefore, the correct answer is the iris (Choice D). Choices A, B, and C contain melanin and are incorrect.

Correct Answer: B

Rationale: Formulating a hypothesis before conducting an experiment is crucial because it helps guide the investigation by suggesting what the investigator should be looking for. A hypothesis serves as a prediction or an educated guess about what might happen in the experiment, providing a clear direction for the research process. It allows the investigator to focus on specific variables and outcomes, making the experiment more organized and effective. Choice A is incorrect because the primary purpose of a hypothesis is not to boost an investigator's reputation but to guide the research. Choice C is incorrect as formulating a hypothesis is not primarily about impressing funders but about setting a clear direction for the study. Choice D is incorrect because the hypothesis is not meant to dictate which results to keep based on preconceived notions but to guide the investigation and allow for unbiased interpretation of results.

Correct Answer: B

Rationale: The most effective technique when defending a scientific argument is to show the results of scientific experiments that support your argument. In the realm of science, evidence-based support is crucial. By presenting concrete data and experimental results, you provide a convincing and reliable foundation for your argument. This method allows others to review, replicate, and verify the findings, thus strengthening the credibility of your position. Choices A, C, and D are not as effective as choice B because citing other scientists who agree with your argument (Choice A) may not carry the same weight as empirical evidence, describing your scientific credentials, education, and past accomplishments (Choice C) may not directly address the validity of your argument, and pointing out that no one has come up with a proven alternative explanation (Choice D) does not provide direct evidence supporting your argument.

Correct Answer: A

Rationale: The most effective procedure in testing whether the drug is responsible for the recovery is to ensure that neither the subjects nor the investigators know which subjects are given the drug and which are given the placebo. This method is known as a double-blind study, which helps eliminate biases and ensures that the results are reliable and not influenced by expectations or beliefs. By keeping both the subjects and investigators unaware of who is receiving the drug or placebo, the study can accurately determine the true impact of the drug on recovery. Choice B is incorrect as it only prevents the subjects from knowing which treatment they are receiving, allowing for potential bias from the investigators. Choice C is also incorrect as it allows for potential bias from the subjects. Choice D is incorrect as full knowledge of treatment allocation can introduce bias and affect the study's validity.

Correct Answer: C

Rationale: Using a computer does not eliminate all subjectivity and potential bias from an experiment. While computers can assist in data collection and analysis, the design and execution of the research study can still be influenced by subjectivity and bias introduced by researchers. Researchers need to recognize their potential biases and take measures to reduce them throughout the research process. Choice A is correct as computers are valuable for managing large datasets. Choice B is correct as computers can efficiently work with instruments and record data. Choice D is correct as computers excel in performing complex calculations faster and more accurately than humans.