What are some of the major obstacles that had to be overcome in uniting the U. S. when building railroads and highways?

Plz which of the following statements about spanish plantations is not accurate? a. spanish plantations grew sugarcane for export to spain b. the spanish had little concerned for the lives of the indians who worked on the plantations. c. spanish plantations grew wide variety of crops and center produce to many different european countries. d. to replace the native americans our dying off the spanish imported african slaves.