What was the purpose of setting four time zones in the continental United States​

What was the overall impact of eli whitneys introduction of interchangeable parts?

How did europeans and africans displace native americans in north america’s predominant peoples?

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.