Read the passage.

Much discussion about the solar system revolves around the status of Pluto as a planet. At one point, Pluto was considered one of the planets revolving around the Sun. Later, it was determined that Pluto is too small to be a planet. Anyone who knows anything about the universe agrees that Pluto should remain labeled as a planet. However, some people still argue that it is just a dwarf planet.

What sentence in the passage contains faulty reasoning?

Much discussion about the solar system revolves around the status of Pluto as a planet.
At one point, Pluto was considered one of the planets revolving around the Sun.
Anyone who knows anything about the universe agrees that Pluto should remain labeled as a planet.
However, some people still argue that it is just a dwarf planet.