The Monument might have been a fallen artifact from a war in Asia.
Migration led to the population of the world because human life started in Africa, meaning that for people to inhabit places that are now known as America, Europe, Australia, etc., they had to all migrate out of Africa.
The annexation of Texas, a slave state, raised a lot of tension because it ruined the balance of power between the North free states and the South slave states.
I think it might be D. Although I am not a genius there were a few Greek uprisings and the Persians had one simple rule that you had to follow, don't ever, EVER betray them.
