The bill of rights was added to the constitution because
key states refused to ratify the constitution unless it was added
alexander hamilton believed it was necessary
it was part of the articles of confederation
it was originally part of the declaration of independence

The Bill of Rights was added to the Constitution because key states refused to ratify the Constitution unless it was added.

Explanation:

The Bill of Rights consists of the first ten additional articles to the United States Constitution. In the context of a free and democratic society - based on the values of the Enlightenment - these guarantee the inhabitants certain inalienable fundamental rights. The Bill of Rights was adopted by the US Congress on September 25, 1789 and ratified by 11 states. This process was completed on 15 December 1791.  

The special meaning of the Bill of Rights results from the connection with the principle of the constitutional jurisdiction, that is, the rights are enforceable of each person before each court of the federation or a federal state, in the last instance before the Supreme Court, also opposite the state Legislators who did not act constitutionally.

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