Why are biologists still debating the classification of protozoans

The biologists have categorized protozoans as a part of Kingdom Protista, they have attempted to sort protists in comparison to three of the other kingdoms, that is, animals, plants, and fungi. However, this has not worked as several of the protists demonstrate features from two or more of these kingdoms.  

The protozoans show considerable diversity, that is, some live as predators, some as parasites, and some others are thriving as producers. Scientists have attempted to categorize the organisms within the protists as either fungus-like, plant-like, or animal-like.  

However, close testing and genetic examination have shown that these classifications often does not imply.  

halogen, any of the six nonmetallic elements that constitute group 17 (group viia) of the periodic table. the halogen elements are fluorine (f), chlorine (cl), bromine (br), iodine (i), astatine (at), and tennessine (ts).

i believe the answer is c