Hi there!
It is C. It isn’t large enough...
Why isn’t Pluto a planet anymore?:
Pluto has only one reason for not being a planet..
It is just too small...
Pluto is now a dwarf planet since it did not meet the three criteria the IAU uses to define a full-sized planet. This means that it doesn’t have the right for people to go on it and it is too small to be also a planet.
Since it‘s too small, it can‘t clear its path and most people can’t even see clearly.