Which project led to the creation of a system of time zones across america?
a. digging the panama canal
b. establishing a national park system
c. building the transcontinental railroad
d. acquiring the territory of alaska

Which effect did the united states supreme court's decision in plessy v. ferguson have? 1. ending segregation in all public schools in america 2. protecting voting rights for african americans by eliminating literacy tests 3. upholding the rights of all citizens to be treated equally by the government 4. authorizing the system that kept black and white people separated