This event is called A-The Long March. Great Leap Forward was a program that Mao introduced once he was Chairman. Trail of Tears was in the US and that was the forced march of Native Americans.
Because there will always be water on earth, meaning that the cycle will never stop. And because the cycle is continuous and natural. I don't think anything can stop it from happening.
It's "C) Surfaces with higher pH levels protect lichens from acid rain."
