Final answer:
Hidden lines identify parts of the structure that are not visible on the drawing.
Step-by-step explanation:
Hidden lines identify parts of the structure that are not visible on the drawing. These lines are used to represent features such as internal sections or hidden edges that would be obstructed in a 2D drawing. They are usually shown as dashed lines to differentiate them from visible lines. For example, in architectural drawings, hidden lines are used to show the location of plumbing pipes behind walls.
The correct answer is A) Hidden lines.