Pluto's status was changed from a classical planet to a dwarf planet primarily because of its:
A) lack of an atmosphere
B) small mass
C) large distance
D) ice-covered surface
E) many moons.

Question

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Pluto's status was changed from a classical planet to a dwarf planet primarily because of its small mass. When it was first discovered, it was thought to be larger than it actually is. However, later observations revealed its relatively small size, leading to the reclassification.

Pluto's Status Was Changed from a Classical Planet to a Dwarf