Why was slavery the main cause of the civil war? Please help

Which statement from the declaration of independece best reflects the enlightment ideas of popular sovereignty

Which of the following world and national events led to a new view of people with disabilities in the us:     a.  world war i and ii veterans with disabilities returned home after the wars.b.  john f. kennedy was elected president and had a sister with a disability.c.  the civil rights and feminist movements.d.  all of the above.

As nation-states began to arise in europe, who became the most powerful individuals?