Correct Answer: D

Rationale: The passage does not suggest that Olympic runners ran barefoot before 195o.

Correct Answer: D

Rationale: The primary purpose is to analyze the various aspects of concussions.

Correct Answer: C

Rationale: The correct answer is C: Regulating leptin, an appetite-controlling hormone. In the provided passage, it is stated that human growth hormone (HGH) is essential for regulating metabolism, building muscle, facilitating calcium retention, and stimulating the immune system. However, leptin is not mentioned as directly regulated by HGH. Instead, the passage discusses how inadequate sleep can lead to lowered levels of leptin, affecting appetite control. Choices A, B, and D are all roles of HGH explicitly mentioned in the passage, making them incorrect answers. Therefore, C is the correct choice as it was not directly linked to HGH in the passage.

Correct Answer: D

Rationale: The passage never says whether or not the CDC succeeded in its original mission (choice A) or whether it continued to be led by doctors (choice B). Inferring either of those things would be a leap unsupported by the text. Choice C is countered by information in the final

Correct Answer: A

Rationale: The tone is appreciative of the work and impact of the CDC over time.