How did the founding fathers strengthen the central union of the united states

The founding fathers build up the central union by creating the Constitution.

Explanation:

By forming the Constitution for the country, the Founding Fathers build up the central union of the United States. Even the Articles of Confederation was adopted in November 15 1777, but it did not put into practice before March 15 1781. After Articles being adopted and Constitution being made, each states of US conducted their own state operations and had their own jurisdiction but what held them together was the principles of Constitution that make them as one nation.

the 2nd option is the answer

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