Two most important factors were the development of industry and industrialization, and the slave trade. People started accumulating large amounts of wealth due to these two and started investing them in businesses, both personal and by other people. This led to the development of capitalism not only in Europe, but other places too.
The nullification crisis was a dispute over the power of the states to reject unconstitutional federal laws.
I would say that B is the most accurate. This is because:
Pull factor is something that makes someone want to <em>arrive </em>in a new country.
Push factor is something that makes them want to <em>leave </em>an old country.
B states that fighting in a homeland, something that a normal civilian wouldn't want to take part in, would make someone want to <em>leave</em> their country.
So, the answer is B!
Because of the german refuse too stop the submarines restriction policy which kept blowing up our ships.
