How did the expansion of railroads accelerate the second industrial revolution in america?

What would lead a historian to consider two events to have a relationship of correlation rather than causation

Me < 3 there are multiple ‘3rd party’ political parties in the us. what are the benefits of having 3rd parties? what are the disadvantages of being a member of one? would the u.s. benefit if there were more 3rd parties created, more support for the current ones, or would it be best to get rid of them altogether? why?

Which is likely the most serious problem associated with an epidemic? 1. there are sometimes no cures to the diseases that spread. 2. people often die from the diseases that spread. 3. there are usually no ways to prevent people from getting ill. 4. people often don’t know they have a disease.