Attempts by Congress to Regulate Child Labor and Factory Conditions

Attempts by Congress to regulate child labor and factory conditions in local workplaces were struck down by the Supreme Court as unconstitutional in the late nineteenth century because regulating local workplaces was

A) perceived to violate the Twenty-First Amendment to the Constitution.
B) perceived to violate the comity clause of the Constitution.
C) was beyond the scope of interstate commerce at the time and was therefore perceived to be an unconstitutional exercise of power by the federal government.
D) perceived to violate the strongly held value of regulated federalism.