Which cue suggests that distant objects appear more densely packed?

The correct choice is texture gradient. This cue arises from the way the surface texture of objects appears to change as they recede into the distance. As objects get further away, the details of their texture become less discernible, making them appear smoother and more densely packed together. The visual difference in texture density gives the perception that objects are closer to the horizon or background merge into one another, reinforcing the sense of depth in a scene.

In contrast, other cues like linear perspective relate to the convergence of parallel lines as they recede into the distance, creating a vanishing point. Relative brightness deals with how the light and shadow on objects can indicate their distance from the viewer but does not specifically address how texture impacts perception. Interposition refers to the way closer objects can block or occlude the view of objects further away, but it doesn't convey the notion of texture density in the same way that texture gradient does. Understanding these distinct cues allows for a better grasp of depth perception in visual environments.