What describes the change in angle between two original perpendicular line segments?

The correct response pertains to the concept of shear strain. Shear strain is described as the change in angle between two originally perpendicular lines. This reflects the deformation that occurs when a material is subjected to shear stress, causing these lines to rotate relative to each other.

In contrast, angular deformation refers to the general change in shape, which is not exclusively associated with the original perpendicularity of the segments. Linear strain measures the deformation in terms of axial length change but does not account for angular changes between segments. Axial strain is focused on the extension or compression of materials along an axis and does not involve any angular change.

Therefore, shear strain accurately represents the scenario described in the question as it specifically addresses the alteration of angles between two perpendicular line segments under shear conditions.