Library.

“Pluto is classified as the ninth planet of the Solar System.”

Pluto is officially classified as a dwarf planet, not the Solar System’s ninth planet. The IAU changed its classification in 2006 after adopting a definition under which Pluto does not clear its orbital neighborhood. Although Pluto was formerly known as the ninth planet, the Solar System’s current official count is eight planets.

“Venus is the only planet in the Solar System that rotates clockwise (i.e., has retrograde rotation).”

Venus is not unique in this respect. Standard references from NASA and ESA state that both Venus and Uranus have retrograde rotation, so the claim’s use of “only” is incorrect. Any attempt to exclude Uranus depends on a nonstandard distinction about axial tilt rather than the ordinary scientific classification.

“Olympus Mons on Mars is the largest volcano in the Solar System.”

Current scientific references support this claim. Multiple authoritative NASA and JPL sources explicitly identify Olympus Mons as the largest volcano in the Solar System, and no credible evidence in the record disputes that conclusion. Minor qualifiers such as “largest known” reflect normal scientific caution, not a real challenge to the claim.