The correct answer is - C) relic borders.
The relic borders are borders that no longer exists, thus they are a thing of the past. In the past they were dividing two countries, but in the present they are not, so they are just reminder of a certain time in the history.
There's numerous examples of relic borders around the world, with the Berlin Wall being the best known of them. The Berlin Wall was a boundary that was superimposed, thus set up by a greater authority, neglecting the people that were living there. This border was dividing Germany into West and East Germany after the World War II, and it only stopped to exist at the beginning of the 90's. Since the border was taken down, it became a relic border, as it no longer exists, but it was a line of division in the past.
