B the I think the answer is b
The correct answer is either manifest destiny or the civil war
Because of the civil war and the expenses of maintaining a navy that could blockade Confederate ports, the Navy was constantly losing power and ships and after the war ended most of the 700 initial ships were completely out of service. As manifest destiny and reconstruction began spreading, the government did not focus on rebuilding its navy and a large part of the navy that remained had to focus on things like helping merchants or doing civilian runs in order to be sustained.
I believe the answer you are looking for is the homestead act of 1862
One of the major ways in which the European Union affects the rest of the world is that it allows for expedited trade to take place between European nations, which brings down the price of various products, which subsequently helps the world economy grow.
