A biological community of interacting organisms and their envious
Northern Ireland is separate from Ireland because 90 years ago people living in Ireland had a war against the British rulers. That's how Northern Ireland split from Ireland.
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A. Korea the U.S tried to stop the spread of communism in Korea. It was divided to the US and the Russians. <span />
1. gravity keeps the water moving downward or just in general
2. the water has to move across the surface for so long till eventually it just erodes away.
those are the only two i know sorry.