Italy is the modern country
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Both presidents at the time were republican
Answer: This region is one of the world's premier natural showcases for Earth history. These rocks formed deep beneath the surface of the earth and were uplifted, eroded, and exposed for eons. By 600 million years ago North America had been eroded to a remarkably smooth surface.
Explanation:
Although all of the options are important factors to determine social movility, I beleive that one amongst them has more impact. Social class at birth makes a significant difference. It is like a stating point in life, some people start with some advantages (like being born in a wealthy and educated family) and other with disadvantages (being born in a poor family with no access to education).
Although race or ethnicity and gender are important too, they can have a stronger or weaker impact depending of your social class. A person that forms part of a minority, for example, african american, will have a very different life depending on the economic situation of the family.
It is true that hard work and education is also needed but, again, social class can lead you to a more familiar and direct contact with them.