I think the answer is b - the bombing of Pearl Harbor
I would say A would be your best option
The mobility of the colonist forced colonial governments to be a liberal because the colonist were always on the move and they wanted to please the colonist that were coming in and have an open mind. The first colleges found it in the American colonies were bite we're by England men OK British men so that is how that happened and the factors that made public education important and most of new England colonies is that they wanted people to know their stuff and be educated..
To stop the spread of communist after World War II, the United States established a policy known as the Truman Doctrine.