What feature can serve as a handrail while navigating?

The correct choice is linear features like rivers or walls because these elements provide clear, continuous pathways that can help guide navigation. Handrails in navigation refer to features that can be consistently followed, allowing for easier movement and orientation within an environment. Rivers are particularly useful as they often lead directly to key locations or endpoints, while walls provide a more man-made guideline that can help individuals stay oriented in urban areas or other developed environments.

Mountains can also provide some guidance, but they are not continuous and can create barriers rather than pathways. Highways serve as significant features in navigation but are less reliable in terms of offering direct routes for someone not traveling by vehicle. Skyscrapers, while visually prominent, do not offer the same dependable guidance as they can be located remotely from pathways and lack the continuous directional assistance that rivers or walls provide. Thus, linear features like rivers or walls are the best choice for serving as effective handrails during navigation.