I believe the answer is A but i could be wrong, during the Civil war it made it easier for them to speak and talk to each other during that time sending goods and messages across the united states.
Hope this helps.
They adopted Christianity because it was the same religion as they're European masters at the time.
Hitler took great trouble to make sure that young people were loyal to him and the Nazi Party. He realized that in the future he may have to call on these people to put up with hardships, to fight and perhaps die for him. Therefore, it was important for young people to think that Hitler and the Nazis were the best thing that had ever happened to Germany.
Youngsters were indoctrinated (brainwashed) to think like the Nazis. Textbooks were rewritten to get across the Nazi message. Children were also taught to recognize Jews at a glance.
I would have to go with Completion of the transcontinental railroad in 1869