OG8 阅读 Q31

Choice D is the best answer. The bottom graph illustrates the process described in the first sentence of the seventh paragraph of the passage: "as the microscope pulls away from the salt, the salt stretches." On the graph, the stretching of the salt is represented by the amount of force, in micronewtons, exerted on the microscope tip as the tip moves away from the salt surface. The graph shows that force was exerted on the tip until the tip reached point T at approximately 22 nanometers from the salt surface; from point T on, the force was 0 micronewtons. It can be inferred that since no force is being exerted after point T, point T is the point at which a salt nanowire breaks.
Choices A, B, and C are incorrect because the labels P, Q, and R all appear on the top graph, which represents data on the movement of the microscope tip toward the salt surface. As the fifth sentence of the fifth paragraph explains, when the microscope tip moved toward the salt, "the salt actually stretched out to glom on to the microscope tip." Therefore, the first graph shows the salt attaching itself to the microscope tip and forming nanowires, not the breaking of a nanowire.