Answer:
B. Pluto's orbit is not clear of other objects
Explanation:
Pluto is a dwarf planet and considered as ninth planet of the solar system.
A large body whose orbit do not clear the neighbourhood is classified as a dwarf planet. The gravity of Neptune limit the orbit of Pluto and shares its orbital neighbourhood with many Kuiper belt objects.
Hence, the correct answer is "B. Pluto's orbit is not clear of other objects".