The astronomical designation of the asteroid named after Pandora is 55 Pandora. It is a large main-belt asteroid discovered in 1858 by George Mary Searle at the Dudley Observatory in Albany, New York.
55 Pandora orbits the Sun in the asteroid belt between Mars and Jupiter. Its name refers to Pandora from Greek mythology, continuing the long tradition of assigning classical names to minor planets.
This object is separate from Pandora, the moon of Saturn discovered by Voyager 1 in 1980. The number 55 is part of the asteroid’s official numbered designation and indicates its place in the sequence of numbered minor planets, not its discovery year or size ranking.
The wrong answers are also names of numbered asteroids, which makes them plausible in a catalog-based question. However, Europa, Ausonia, and Asia have different numbers and are distinct minor planets.