Final answer:
Among the options provided, layers of the earth can be considered concentric because they consist of multiple layers, each sitting inside the other with a common center.
Step-by-step explanation:
Among the given options, layers of the earth would be considered concentric. This is because they are like multiple layers within a spherical object, each layer sitting inside the other, much like the layers of an onion. Concentric objects share the same center, axis, or origin, with one object inside the other, often having different radii. A clear example is a cross section of Earth, as shown in Figure 12.1.1, displaying various layers such as the crust, mantle, outer core, and inner core.
Other examples of concentric objects can include an artificial satellite orbiting the Earth, a race car moving in the circular race track, and a ball tied to a string being swung in a circle around a person's head, where each of these follows a path around a common central point. However, these examples illustrate objects in motion rather than static concentric layers.