Which of the following is a true statement about the map?

the border between canada and the united states is a thin, blue line; this indicates an international boundary.
the border between mexico and texas is a thick, black line; this indicates a river boundary.
the border between mississippi and arkansas is a thin, black line; this indicates an international boundary.
the border between mississippi and arkansas is a thin, blue line; this indicates a natural river boundary.