Random attacks by Indian tribes. The frontier had swamps-to-mountainness terrain. Seeds didn't work in all parts of America, some lived healthy in one area while the same seed could die somewhere else there.
Answer: Don't Listen to the other answers. The Washington Monument in D.C. is an Obelisk modeled after ancient Egyptian Monuments.
Explanation:
They used the technology in conquests to expand the empire.
A. Natural disasters, such as tsunamis, earthquakes, and floods
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It was primarily" "high mountain ranges" that was the physical barrier that helped separate ancient China from Southeast Asia, since these were very difficult to traverse. <span />
