The reclassification of Pluto as a dwarf planet resulted from failing which specific IAU requirement?

Answer

Clearing the neighborhood around its orbit

Pluto's reclassification stemmed specifically from the strict 2006 ruling that required a planet to be gravitationally dominant, a criterion Pluto does not meet.

The reclassification of Pluto as a dwarf planet resulted from failing which specific IAU requirement?
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