The southernmost point to which glaciers advanced in North America is marked by the path(s) of the

Ohio River. Missouri river

Explanation:

The historical evidence clearly indicates that the Ohio River did not exist before the last ice advances. Before Ohio and Missouri rivers, the major glacier drainage of the east-west direction happens in the Teays River. When the ice of the glaciers blocked the Teaya river valley, then Ohio was formed.

Like Ohio, the Missouri river did also not exist before the Pleistocene and during that time the largest drainage in North America takes place in the Hudson's Bay

the correct answer on edgen is:

(c.) prevent the spread of communism.

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