Answer:
B. The growth of the railroads increased the demand for natural resources.
Explanation:
Railroad transportation changed the way American people traded. For instance, agriculture products were transported easily throughout the country.
The completion of the Transcontinental Railroad greatly affected companies that made products in that it made it far easier for them to transport their goods over long distances to markets, which greatly increased profits and output.
Communist northern Korea invaded non-communist southern korea, and the U.S. intervened because they hate everything communist and because southern Korea was an ally; this was the first hot war of the Cold War
I think that these are the answers for your questions.
3. B
4. B
Advantages:
From a conservative or state-based ideology: it is much easier to control population since they rarely receive "strange" ideas or influence from outside. Domestic policies become much more important. In so, it becomes easier to set popular aims targeting citizens.
The country could(historically seen) stand the best defense against outside powers which could try to set an invasion. For example, the Great Wall of China turned out to set a strong defense against Mongols and other menaces along many centuries.
Disadvantages are listed:
Trading with other countries can influence negatively on economic growth, as there is no autonomous country even if it results as big as China.
Trade has become key in today's globalized world, henceforth the need to collaborate or cooperate in economic exchanges is a necessity to keep up the pace in global affairs.
