What is the main idea of the passage?

Correct Answer: C

Rationale: The main idea of the passage is that innovations and improvements in bicycle design have made bicycles one of the most popular means of recreation and transportation worldwide. The passage outlines the evolution of bicycles from their early designs to the modern versions, emphasizing how these changes have contributed to their popularity. Choice A is incorrect because it focuses only on the current status of bicycles, while the main idea encompasses the evolution and improvements in design. Choice B is incorrect as it mentions the invention of the first modern bicycle but does not address the overall impact of innovations on bicycle popularity. Choice D is incorrect as it simply states a fact without capturing the essence of the passage, which is about the impact of design improvements.

Correct Answer: B

Rationale: Macmillan added iron rims to his bicycle tires to enhance their durability and make them last longer. This innovation aimed to prevent the tires from getting worn down quickly. Adding weight to the bicycle (Choice A) was not the purpose of adding iron rims. While adding iron rims could potentially reduce the bumpiness of the ride (Choice C) by providing more stability, the main objective was to improve tire longevity. Similarly, reducing the level of fatigue during the ride (Choice D) was not the primary reason for adding iron rims.

Correct Answer: C

Rationale: The correct answer is C. The passage aims to provide an overview of cystic fibrosis (CF) and how it is inherited. It explains that CF is passed down through families due to a defective gene, detailing how this gene affects the body and who is most commonly affected by the disease. Choices A, B, and D are incorrect because the passage does not solely focus on describing the causes of CF, explaining how it is passed down through families, or reviewing why some Americans have CF while others do not. Instead, it provides a broader perspective on CF and its inheritance.

Correct Answer: D

Rationale: In the context provided, 'defective' means faulty, referring to the gene that causes cystic fibrosis (CF). The passage explains that CF is caused by a defective gene, resulting in the production of abnormally thick and sticky fluid. The word 'defective' suggests that the gene is not functioning correctly, leading to the symptoms associated with the disease. Therefore, 'faulty' is the correct choice. The other options, 'unusual,' 'remarkable,' and 'postponed,' do not accurately capture the meaning of 'defective' in this context and are therefore incorrect.

Correct Answer: D

Rationale: Strauss set up a net to ensure the safety of the workers in case of falls during the construction of the Golden Gate Bridge. Safety nets were essential to protect the workers from potential accidents or falls while working on the bridge. Choice A ('For suspension') is incorrect as safety nets were not used for suspension purposes but rather for worker safety. Choice B ('For balance') is incorrect as the balance of the bridge was maintained by other construction elements, not safety nets. Choice C ('For aesthetics') is incorrect as safety nets are not related to the visual appearance of the bridge but rather to the protection of the workers.