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: D

Rationale: The correct answer is D because the passage specifically states that at the nanoscale, unique properties of materials emerge, which is a key benefit of nanotechnology. Choice A talks about what scientists can do but does not directly describe the benefits mentioned in the passage. Choice B is the definition of nanotechnology and not a specific benefit. Choice C mentions the use of different colors in medical tests, which is a specific application rather than a general benefit of nanotechnology.

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: The best title for this passage would be 'A ride through the history of bicycles' as it provides a comprehensive overview of the historical development of bicycles from their invention to modern times. Choice A, 'Bicycles are better,' is incorrect as it does not capture the essence of the passage, which focuses on the history and evolution of bicycles rather than their superiority. Choice C, 'Cycle your way to fitness,' is misleading as the passage does not primarily discuss the fitness aspect of cycling but instead focuses on the evolution of bicycle design. Choice D, 'The popularity of bicycles,' is too narrow as it only touches on one aspect mentioned briefly in the passage, while the passage covers a broader historical perspective.

Correct Answer: B

Rationale: The correct answer is B. Matter at the nanoscale exhibits unique and special characteristics that distinguish it from matter at larger scales. This can include properties like increased surface area, different melting points, altered conductivity, and enhanced reactivity. Choice A is incorrect as metals at the nanoscale can be more rigid compared to their larger scale counterparts. Choice C is incorrect because matter at the nanoscale has properties that are distinct from both atomic and larger scales. Choice D is incorrect as there are significant differences in how matter behaves and interacts at the nanoscale compared to larger scales.