What element of the military terrain refers to areas that hinder movement?

The term that refers specifically to areas that hinder movement in military terrain is accurately identified as obstacles. Obstacles are natural or man-made features that control or impede movement, presenting challenges for personnel and vehicles. These can include rivers, dense forests, urban areas, or fortifications, effectively restricting the routes that forces can take to maneuver.

Key terrain, on the other hand, denotes areas that, if seized or controlled, would provide a significant advantage to forces. Avenues of approach identify the paths from which an enemy can advance into a position. Cover and concealment refer to elements that protect forces from detection and fire while allowing them to maneuver. Thus, obstacles are the most precise descriptor for areas that specifically hinder movement on the battlefield, making this choice correct.