It would be more appropriate to use the word boundary than its synonym edge when describing a.) an edge on a map b.) an edge of a ruler. c.) an edge of a scarf. d.) an edge on a street sign

A.) an edge on a map.

Explanation:

This is the most appropriate case in which to use the word "boundary." A line that sets a limit on a map (for example, to limit the extent of a country) is called "boundary." It can also be called "border" or "frontier." Although the word "edge" is often a synonym, it cannot be used in the same way in this particular case.

could you provide an image?