Answer:
Pluto is known as dwarf planet because it has not cleared the neighborhood around its orbit
Step-by-step explanation:
Pluto is not considered a planet any more and it is called a dwarf planet because it does not meet one of the international astronomical Union criteria which is " it has not cleared it's neighbouring region of other object" which indicate that it has no gravitational dorminancy and it's tend to share it's orbital space with other neighbouring objects of the same size.
Pluto has mountains, glaciers and thin atmosphere.