For What Reason Was Pluto Demoted from Full Planetary Status

Multiple Choice

For what reason was Pluto demoted from full planetary status in 2006?

A) because of objects as large or larger than Pluto in the Kuiper belt
B) because Pluto resides outside of the zone that can truly be described as the solar system
C) because Pluto was discovered to be a twin planet system
D) because according to the standard definition,no planet can be smaller than the Earth's moon