Answer :
Based on the historical account, the Northwest Ordinance was passed "under the Articles of Confederation."
This is evident in the fact that the Northwest Ordinance was passed on July 13, 1787, by the Confederation Congress, under the Articles of Confederation.
The Northwest Ordinance served or listed out the procedure for admitting new states to the Union.
Hence, in this case, it is concluded that the correct answer is option B. "under the Articles of Confederation."
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