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

America's railroads began using a standard time system involving four time zones, Eastern, Central, Mountain and Pacific

Explanation:

I used the the History Channel website and I got the question right on a test

- "schenck v. united states, case in which the u.s. supreme court ruled on march 3, 1919, that the freedom of speech protection afforded in the u.s. constitution's first amendment could be restricted if the words spoken or printed represented to society a “clear and present danger.” "

- speech aimed to potentially create danger could be banned.

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social contract theory, nearly as old as philosophy itself, is the view that persons' moral and/or political obligations are dependent upon a contract or agreement among them to form the society in which they live