Answer:
are there answers for the question?
Explanation:
The correct answer for the question that is being presented above is this one: "B. building of the transcontinental railroad --> disappearance of the frontier." The pair of events that did the first event most directly influence the second is the building of the transcontinental railroad --> disappearance of the frontier.
I say B because then they would be able to tell how much pages of homework and how long it would take them.