What problem was caused by southern farmers grow and tobacco
year after year

Pretty sure the crops started to become smaller and lower in quality each year after another.

Explanation:

I looked it up

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.