Why has the kingdom Protista been abandoned?

Why has the kingdom Protista been abandoned?

A.) Some protists are multicellular.
B.) The kingdom Protista is polyphyletic.
C.) Some protists are more closely related to plants, animals, or fungi than they are to other protists.
D.) Some protists are as small as prokaryotes.
E.) The second and third answers are correct.
I picked C, but Pearson said "This is true, but there is a better answer."

Answer:

image