Maria is on the viewing deck of a very tall building and she notices that objects in the distance appear hazy in comparison to objects that are close. maria is using the depth cue of

Maria is perceiving the Aerial Perspective also called Atmospheric Perspective. This refers to the perception we have when observing an object at a distance, this effect occurs due to the pressure exerted by the atmosphere on an object that is seen at a great distance. This affects how we see the details and colors of the object. In this case, the building that Maria sees.

Maria is using the depth cue of aerial perspective.
Aerial perspective or atmospheric perspective is a term referring to the visual effect of viewing an object from a great distance. The effect is caused by the presence of the atmosphere and intensifies as the distance from the object increases. Its general characteristics include the decrease of the contrast between the object and the background, the objects appear hazy and the colours are less saturated.