Can anyone help I already know the answer I just wanna make sureee!

Blue:)

Explanation:

i think the answer is c, rivers.

explanation:

sometimes, borders fall along natural boundaries like rivers or mountain ranges. for example, the boundary between france and spain follows the crest of the pyrenees mountains. for part of its length, the boundary between the united states and mexico follows a river called the rio grande. the borders of four countries divide africa’s lake chad: niger, chad, cameroon, and nigeria.

. political or economical policy that isolates a country from participating in international relationships. it has been suggested that the united states participates in isolationism because of its lack of involvement in particular wars or alliances.