Which phrase describes what the "push and pull" theory was about?

About the migration of people to the America is the correct answer.

Explanation:

There were push and pull factors that led to migration of people to America. The main factors were religious, political and economic. People migrated to avoid war and religious persecution and some came to find jobs in USA. In Europe the pilgrims were persecuted for their beliefs while the US was growing and developing there were ample opportunities and jobs. Although the immigration was not always constant, the immigration developed rapidly between 1870 and 1900, during this time most of the immigrants were from China and Europe , a small number also migrated from Korea and Japan.

answer; /// i do believe that its napolean's conquest of spain;

1. darius the great     persia  

2. piankhi       nubia

3. ezana       aksum

4.     nebuchadnezzar     babylonia

5. shalmaneser iii     assyria