Final answer:
During World War I, a majority of the U.S. Navy's ships were part of the Atlantic Fleet. In the context of building an American empire, Mahan did not see the need for the reopening of the American frontier, but rather focused on a strong navy and acquiring military bases. To ratify an amendment to the U.S. Constitution, three-fourths of the states must agree.
Step-by-step explanation:
During World War I, a majority of the Navy's ships were assigned to the Atlantic Fleet. This strategic choice was influenced by America's need to participate in the maritime security and convoy systems established to protect merchant vessels from the German U-boat threat in the Atlantic Ocean. While the United States maintained an isolationist policy throughout the 19th century, the early 20th century brought about a change, partially influenced by Alfred Thayer Mahan's theories on the importance of naval power. However, even with this shift towards a larger naval presence, the majority of the U.S. military force remained small compared to European powers, until the expansion induced by the U.S. entry into the war and later the attack on Pearl Harbor. In contrast to this, Mahan did not believe that the reopening of the American frontier was needed to build an American empire. His emphasis was on building a strong navy and acquiring military bases around the world, which would provide the necessary power projection to support an empire. A canal through Central America—such as the Panama Canal—was also seen as essential to support a global naval strategy. When it comes to the ratification of amendments in the United States, the requirement is that three-fourths of the states must ratify an amendment before it becomes law. This amounts to having 38 out of 50 states in agreement for an amendment to be added to the Constitution, providing a balance between widespread national consensus without necessitating absolute unanimity.