Why do I keep chewing on plastic straws?

Because once you try something and you like it, you will be addicted to it and you'll do it as much as u want.

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.

i would say your answer is a)

sorry if im wrong