The part of the passage that BEST demonstrates the great ignorance in the United States of the North American continent west of the Mississippi River is D. the suggestion that there might be a water route to the Pacific Ocean.
Before the Louisiana Land Purchase from France by President Thomas Jefferson, it was not obvious to the United States that the Mississippi River provided a route to the Pacific Ocean.
The great ignorance is not demonstrated by
Thus, great ignorance is demonstrated by D.
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