The Discovery of Eris

The discovery of Eris

A) was surprising,since we thought we knew about all large objects in the solar system.
B) was not surprising,because other Kuiper belt objects approaching the size of Pluto had already been discovered.
C) was surprising,due to its "backwards" orbit around the Sun.
D) was not surprising,because the existence of a massive "Planet X" had been predicted nearly a century ago.