Pluto was originally classified as a planet, but new criteria for the definition of a planet were adopted, and Pluto failed to meet one of them. Which one?
A) Pluto does not orbit the Sun directly.
B) Pluto does not have enough mass to pull itself into a roughly spherical shape.
C) Pluto does not spin fast enough to produce its own magnetic field.
D) Pluto does not have enough gravity to clear its orbit.

Question

Quizplus · Accepted Answer

Pluto was reclassified as a dwarf planet because it does not have enough gravity to clear its orbit of other debris and objects, which is one of the criteria set by the International Astronomical Union (IAU) for a celestial body to be considered a planet.

Pluto Was Originally Classified as a Planet, but New Criteria