Question

which organization reclassified pluto as a dwarf planet?
the international astronomical union (iau)
the national aeronautics and space administration (nasa)
the international space station team (iss)
the european space agency (esa)

Explanation:

The International Astronomical Union (IAU) is the global authority for defining celestial body classifications. In 2006, it established the definition of a planet, which led to Pluto being reclassified as a dwarf planet. Other options (NASA, ISS team, ESA) are space agencies or operational teams, not responsible for astronomical classifications.

Answer:

the International Astronomical Union (IAU)