Children were used for cheap labor
<span>The invention of new communications technology.
</span><span>Improvements to shipping technology
</span>
National defense may be at risk due to free trade
This depends on if a refers to the current government.
If it is, then the answer is D. none of the above
However, the articles of confederation, america's first government, was the first thing that Americans did after the war, so the answer could also be A
The technology, logistics, and communication of the north that allowed them to defeat the south is because of their skill of having to manufacture supplies and weapons that they need for the war. They were able to create more weapons and be able to hire more soldiers.
Hope this helped :)
Have a great day