Astronomers Have Been Searching for Additional Planets, Especially Since the Discovery

Multiple Choice

Astronomers have been searching for additional planets, especially since the discovery of Uranus in 1781. But why were efforts concentrated around 2 to 3 au from the Sun in the early nineteenth century?

A) Kepler's third law predicts a planet within this distance.
B) The Titus-Bode law predicts a planet within this distance.
C) The discrepancies in Uranus's orbit suggested a planet around this radius.
D) The telescope, newly invented in 1781, was not powerful enough to detect anything beyond this range.