The correct answer is A. banning of child labor.
The federal minimum wage is not established until the 1930's, almost a decade after the Progressive era ended.
The banning of workplace discrimination based on race was not passed until the Civil Rights Act of 1964.
However, during the Progressive Era, child labor started to slowly but surely become outlawed. Different states started to outlaw the idea of child labor as early as 1902. Gradual banning of child labor continued state by state, and ultimately resulted in the complete banning of child labor in the early 1930's.