What key characteristic do non-isometric lines lack?

Non-isometric lines are characterized by their inability to be defined by true lengths without finding their endpoints. In isometric drawings, lines are represented at angles that allow for true measurements and relationships to be maintained. However, non-isometric lines do not adhere to this principle, as they appear distorted and do not maintain consistent length representations when depicted on a two-dimensional surface.

The misunderstanding regarding this concept often stems from imagining how lines can be represented or drawn on a paper. Non-isometric lines cannot be measured directly or drawn using predefined lengths like isometric lines, as they do not retain their true length appearance. This characteristic makes it necessary to identify their endpoints to ascertain their real-life dimensions, distinguishing them clearly from isometric lines.

In contrast, the other options do not accurately capture the defining traits of non-isometric lines. They can certainly be drawn with a ruler, do not need to be perpendicular to other lines, and are not always parallel to any particular axes. These inaccuracies clarify why they do not address the essence of what sets non-isometric lines apart.