Question

1. what is the reason plutos classification changed from planet to dwarf planet?

bodies in the same area as pluto are not under its gravitational pull.
pluto no longer has enough mass to be round in shape.
pluto no longer orbits the sun.
pluto has moved outside of the milky way galaxy.

Explanation:

According to the International Astronomical Union (IAU) definition of a planet, one of the criteria is that it must have "cleared the neighborhood" around its orbit. Pluto fails this criterion as there are other objects in its orbital region that are not gravitationally dominated by it. Pluto still has enough mass to be round (so the option about mass and shape is wrong), it still orbits the Sun (so the option about orbiting the Sun is wrong), and it has not moved outside the Milky Way galaxy (so the option about the Milky Way is wrong).

Answer:

Bodies in the same area as Pluto are not under its gravitational pull.