I believe the answer is basal sliding
Answer:
a nuclear weapons treaty (nuclear non-proliferation)
I believe the correct answer from the choices listed above is the last option. All spheres of earth are interrelated or interdependent. This means <span> an impact to one sphere usually affects another one cannot exist without the other. Hope this answers the question. Have a nice day.</span>
A biggie: the transcontinental railroad. Because it would economically improve wherever it was, both the North and the South competed for the railroad to be in their respective territory, evidenced by the Kansas-Nebraska Act and the Gadsen Purchase and induction of California as a free state in 1860.
In addition: people could get land cheap because it was abundant and might leave to start afresh economically.
There's other stuff I can't remember as clearly, but there's a little and I hope it helps :)
