What are the stages civilizations go through

Space is not completely empty. there are small particles in space. what happens when these particles come together?

Which of the following was probably the most difficult challenge facing construction of the railroad?

Part a: which statement identifies the central idea of the text? a: the north was more powerful than the south and was always going to be the victor of the civil war. b: despite the obvious strength of the north, the outcome of the war was unpredictable at the time. c: the united states underestimated the strength of the south, giving it the upper hand. answer !