Question

question 3 of 5
when was pluto formally downgraded from planet to dwarf planet?
a. after the hayden planetariums solar system exhibit opened
b. after a vote by the international astronomical union
c. after dr. tyson received a letter from a concerned child
d. after the new york times published an article about pluto

Explanation:

In 2006, the International Astronomical Union (IAU) voted on a new definition of a planet. As a result of this vote, Pluto was re - classified as a dwarf planet.

Answer:

B. After a vote by the International Astronomical Union