Correct Answer: A

Rationale: The correct conclusion that can be drawn from the passage is that it is advisable to choose unsaturated fats over saturated fats. The passage emphasizes the health benefits of unsaturated fats, such as lowering cholesterol levels and reducing the risk of heart disease. It also mentions that saturated fats, although not as healthy as unsaturated fats, should still be consumed sparingly. Trans fats are highlighted as the least healthy fats, increasing the risk of heart disease. Choice B is incorrect because the passage does not explicitly compare the caloric density of saturated and unsaturated fats. Choice C is incorrect as the passage does not discuss the caloric density of trans fats in comparison to saturated fats. Choice D is incorrect as the passage states that unsaturated fats are found in sources like olive oil, walnut oil, and avocado oil, not mostly in animal products.

Correct Answer: C

Rationale: The tone of the essay is discouraged as it expresses concern about the U.S.'s lower life expectancy ranking and contributing factors.

Correct Answer: B

Rationale: In this context, "watchdog" refers to a guard or overseer, specifically relating to Lifewings Partners' mission of ensuring safety and preventing medical errors. The organization acts as a monitor in healthcare settings, which aligns with the definition of a watchdog, confirming that option B is correct.

Correct Answer: D

Rationale: The author's tone is disapproving, as evidenced by the focus on the negative consequences of using cosmetics with harmful ingredients. The passage discusses historical and contemporary health issues related to beauty practices, indicating a critical stance on the use of cosmetics that compromise health, which supports option D.

Correct Answer: A

Rationale: The main idea of the passage is that recent discoveries are shedding light on the pivotal role of microorganisms in maintaining a properly functioning immune system. The passage discusses how the human body hosts a wide array of microorganisms, emphasizes the importance of these bacteria in the development of the immune system, and explores the potential applications of bacteriotherapy. Choice A is the correct answer because it accurately reflects the central theme discussed in the passage. Choices B, C, and D are incorrect because they focus on specific details or applications mentioned in the passage, rather than capturing the overarching theme of the critical role of microorganisms in immune system function.