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.

Correct Answer: D

Rationale: The main idea of the passage is that MRSA is a significant issue both within and outside of hospitals. It highlights the challenges posed by MRSA, including its resistance to antibiotics, high mortality rates, and widespread presence in various settings. While the development of new technologies like nanomaterial textiles shows promise in reducing hospital-associated MRSA, the passage also emphasizes the importance of practicing good hygiene to prevent community-associated MRSA infections. Choices A, B, and C are incorrect because they do not capture the comprehensive overview of MRSA provided in the passage. Choice A encompasses the main idea by emphasizing the significance of MRSA and ways to mitigate the risk. Choice B focuses on a specific solution rather than the broader issue of MRSA. Choice C is incorrect as it oversimplifies the risks associated with MRSA strains by only mentioning fatality.

Correct Answer: C

Rationale: The correct answer is C. The passage emphasizes the importance of certain bacteria for a properly functioning immune system. It discusses how harmless bacteria play a crucial role in defending the body against pathogens. Choice A is incorrect as it focuses on the immune system's response to certain types of bacteria in lower organisms, not the overall importance of bacteria for immunity. Choice B is incorrect as it mainly discusses bacteriotherapy in relation to the reconstruction of a damaged colon, rather than the broader role of bacteria in immune system health. Choice D is incorrect as it only talks about the process of replacing harmful bacteria with harmless ones, missing the key point about the necessity of certain bacteria for immune system function.

Correct Answer: B

Rationale: In this context, "conform" means to fit in with societal norms or standards, particularly those related to beauty. The passage describes how individuals may compromise their health to meet these cultural ideals, indicating that conformity relates to adhering to social expectations of beauty, making option B the correct interpretation.

Correct Answer: A

Rationale: The passage suggests that obesity and its related health issues contribute to lower life expectancy, implying obesity is detrimental to a long life.