What was americas unique contribution to manufacturing?

The American system of manufacturing was a set of manufacturingmethods that evolved in the 19th century. The two notable features were the extensive use of interchangeable parts and mechanization for production, which resulted in more efficient use of labor compared to hand methods. The system was also known as armory practice because it was first fully developed in armories, namely, the United States Armories at Springfield in Massachusetts and Harpers Ferry in Virginia (later West Virginia), inside contractors to supply the United States Armed Forces, and various private armories. The name "American system" came not from any aspect of the system that is unique to the American national character, but simply from the fact that for a time in the 19th century it was strongly associated with the American companies who first successfully implemented it, and how their methods contrasted (at that time) with those of British and continental European companies. In the 1850s, the "American system" was contrasted to the British factory system which had evolved over the previous century. Within a few decades, manufacturing technology had evolved further, and the ideas behind the "American" system were in use worldwide. Therefore, in manufacturing today, which is global in the scope of its methods, there is no longer any such distinction.

Ithink the answer is b.)