Why are protists now placed is several groups rather than in one kingdom?

A)Because it was discovered that there were both single and multi-cellular protists.
B)Because protists are the most abundant organisms on earth.
C)Because protists were discovered to be both eukaryotic and prokaryotic.
D)Because some protists use DNA as their genetic molecule and other protists use RNA.
E)Because it was determined that some protists were more closely related to plants, animals and fungi than other protists.