Dashes are used to emphasize or set off content, while hyphens are used as a single modifier before a noun.
In this question, we are discussing the use of dashes between two proper nouns when a hyphen already exists within the name of either proper noun. The correct option would be a. North—South, where the hyphen in North-South is replaced by a dash to differentiate it from the hyphen already within the territory name. Dashes are used to set off or emphasize content, while hyphens are used to join words serving as a single modifier before a noun.