It was used as a secret code among the slaves.
Answer:c
Explanation:
Hernandez, L. "Flight." Illustration. The Artist's Page. Artists Unlimited, 12 December 2010. Web. 15 May 2012.
It's when you have too much nutrients in a lake or pond mainly from runoff in big rain storms, this can cause plants to grow more than normal and kill the fish in it for lack of oxygen.
