Which act prohibited the shipment in interstate commerce of products manufactured by children under 14 years old?

The correct choice is the Child Labor Act, which was designed specifically to address the exploitative practices of child labor prevalent in the United States during the early 20th century. This legislation aimed to protect children from the dangers and hardships of industrial work by prohibiting the shipment in interstate commerce of products made by children under the age of 14. This was a significant milestone in labor reform, as it reflected growing societal awareness about the need for regulation to ensure the welfare of children and prevent their exploitation in the workforce.

The other acts mentioned, while related to labor and wage standards, did not have the same specific focus on child labor. The Fair Labor Standards Act, for instance, established minimum wage and overtime pay, but it built upon existing laws and did not exclusively target the issue of child labor. The Minimum Wage Act is not a widely recognized piece of legislation; instead, wage regulations are typically addressed within the Fair Labor Standards Act. The Employment Standards Act is also not a specific historical act relating uniquely to child labor issues. Each of these alternatives does not align as closely with the specific provisions of the Child Labor Act, which is why the latter is the most accurate answer.