During the 1800s due to an economic and military weakness of the U.S compared to its neighbors the British, French and European rivals, the United States foreign policy makers sought diplomatic means to counter European presence.
The U.S diplomacy aimed at preventing France and Britain from accessing the control of more colonies in Latin America and Mexico which were a part of a declining Spanish empire.
Foreign policy goals previously focussed on gaining colonies and expansion to new territories, but, changed to developing commercial empires, limit the influence o the Soviet (USSR) and encourage more significant economic and political freedom.
In general, the railroads had a positive impact on the relationship between eastern cities and the Great Plains, since they allowed for the transportation of people and goods between these two areas in ways that were far quicker and more efficient than before.
Answer:
How to Write a Conclusion
Include a topic sentence. Conclusions should always begin with a topic sentence. ...
Use your introductory paragraph as a guide. ...
Summarize the main ideas. ...
Appeal to the reader's emotions. ...
Include a closing sentence.
Explanation:

D. The secession of south Carolina from the Union.