What cost prehistoric people to drastically change the way they lived? a. climate change b. fires c. rivers. d. all of the above

I would say d it a guess

in 550 b.c.e. cyrus the great, the leader of the persians, conquered the medes and united the iranian people under one ruler for the first time. cyrus became the first king of the persian empire and went on to establish one of the largest empires in world.