OG8 阅读 Q22

Choice A is the best answer. The first paragraph explains that in the nanoworld, salt can be seen "stretching like taffy." The third paragraph notes that while this elasticity was expected in metals, it wasn't imagined for salt: "But scientists don't expect this superplasticity in a rigid, crystalline material like salt." The rest of the passage explores this unexpected behavior of salt. Therefore it can be said that one of the central ideas of the passage is that materials don't always behave as scientists might expect them to.
Choices B, C, and D are incorrect because the passage focuses on the unexpected way that salt reacts in the nanoworld, not on the role of inputs and outputs in systems (choice B), the relative strengths and weaknesses of models (choice C), or how the properties of systems differ from the properties of their parts (choice D).