Answer:
Parallax
Step-by-step explanation:
"Parallax" refers to a displacement of an object's position in space (as being seen by an observer) when looking at the object along two varying sight lines. The projection of objects that are near shows a larger parallax than the objects that are farther away.
This is the phenomenon which explains why the road trees in the middle distance seem to shift in a position that is relative to the far away hills.
So, this explains the answer.