Which event ultimately brought about the decline of Mississippian civilizations? the American Revolution
the importation of enslaved workers
the arrival of Europeans
the creation of European settlements

the arrival of Europeans

Explanation:

The arrival of Europeans is the biggest reason for the decline of Mississippian civilizations.

The arrival of early Europeans for trading came with diseases that spread to the natives and due to lack of immunity to new infectious diseases like epidemics, smallpox, and measles, some mississippian migrate to other places and some died due to diseases. Then slowly the European trade destroyed the Mississippian civilizations.

Hence, the correct answer is "the arrival of Europeans".

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