This would be A i am guessing
Answer:
surviving of what they need
A policy of extending a nation power by gaining political and economic control over other nation.
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The Transcontinental Railroad innovation had the GREATEST impact on westward migration immediately after the American Civil War.
After the Civil War, there was great interest and opportunity with westward expansion. With the invention of the railroad, the transport of goods and people became quicker and less expensive than ever before.