Final answer:
A hidden line is a medium that is made up of evenly spaced dashes and is used to show edges that are not actually visible.
Step-by-step explanation:
The correct answer is A. Hidden line. A hidden line is a medium that is made up of evenly spaced dashes and is used to show edges that are not actually visible. It is commonly used in technical drawings or blueprints to represent features that are not visible from a particular viewpoint.