Answer:
I think the answer is option A
The main reason why the United States largely shied away from imperialism prior to 1890 was because there was plenty of potential raw materials and resources located in North America, so the US had no real reason to begin searching in other places like Africa.
The amendment becomes part of the Constitution when it has been ratified by three-fourths (currently 38) of the states. This process has been used for ratification of every amendment to the Constitution thus far. Article V also provides for an alternative process, which has never been utilized.