Corruption. Gilded means covered in gold, but on the inside, it was corrupted. There was economic growth, but there were political machines (industry had too much power) and lots of poverty, which lead to the rise of labor unions. For more information, check out the Wikipedia page on the Gilded Age.
Alliances pretty much started the whole war, it determined who was fighting who basically
The correct is answer is B
Assuming this is referring to the same picture that was posted before with this question, the proper answer is "(4) giving public land to railroad companies to
<span>help finance railroad construction"</span>
