Final answer:
The Articles of Confederation were not merely revised due to their fundamental weaknesses and the need for a more robust central government to address issues like national defense and economic regulation. The correct answer is option C.
Step-by-step explanation:
The leaders of the United States chose not to simply revise or improve the Articles of Confederation in 1787 because they recognized the need for a stronger central government than what was provided by the Articles. The Articles' inability to adequately address critical issues such as defense, taxation, and interstate commerce highlighted its weaknesses. Influential figures like Madison and Hamilton, along with incidents like Shays' Rebellion, demonstrated that the existing system was too weak to effectively govern the nation. Thus, delegates met in Philadelphia and decided to create a new Constitution, which established a federal system with balanced state and national authorities.