Which were results of the construction of the transcontinental railroad? choose all answers that are correct.
a. the railroad cut travel time between the east and west coasts of the united states by many weeks.
b. the railroad allowed the great plains to become the most densely populated region of the country.
c. the railroad made the plains indians wealthy because they owned the land it crossed.
d. the railroad led to the creation of uniform time zones in order to make scheduling trains easier.