Which project led to the creation of a system of time zones across America?

Adigging the Panama Canal
Bestablishing a national park system
Cbuilding the transcontinental railroad
Dacquiring the territory of Alaska

Verified Answer :

It was the "building of the transcontinental railroad" that led to the creation of a system of time zones across America, since allowed for the relatively rapid transport of both people and goods across the US, which required strict coordination.