Which of these is an example of a subsequent boundary? A. Straight lines or arcs are drawn on a map to show the border between two adjacent countries.

B. Steep mountains separated two regions before people settled in them.

C. A wall is built along an existing border to keep people from crossing it illegally.

D. A border is created dividing the North and South of a country because of conflict.

E. A border separating two states is removed because the states are now one state.