I'm afraid I couldn't give you a complete answer, or the answer that you're looking for, for this question regarding the Native-born Americans in 1860's since there is no map provided with this question. Try re-posting this question with the map on it.
The correct answer is A on Enginuity.
Well that would likely hinder the trade for such nation, like China. China has a TON of industry, and what would happen of it couldn't reach outside its borders? The economy would plummet! It would weaken every aspect of the nation.
Answer:
So that there would be more food to go around on the home front
So that soldiers, marines, and sailors would have enough
Explanation:
got it right