In the past, scientists categorized protists into three groups according to whether they were plant-like, animal-like, or fungus-like. Which two statements are the most likely reasons that scientists reclassified protists into six major clades, and no longer use the old system?

A. Many protists do not fit into any of the older subgroups.
B. Some protists reproduce asexually by mitosis, whereas others reproduce both asexually and sexually.
C. Although most protists are unicellular, quite a few are multicellular.
D. Protists display a far greater degree of diversity than any other eukaryotic kingdom.