The key factor of American opportunity is the

Many people view the United States as the land of opportunity because it presents them with life options they may not have had in their countries. Employment that could lead to economic stability is a big draw that foreign-born Americans pursue.

Explanation:

This sorta helps...have a good day!

2018 means 2018 ce or common era

there have been other eras too including bce, which included way more years.

the answer is b just took the test