What problems do biologists have with the kingdom protista?

Lynn Margulis and Karlene Schwartz, in their book The Five Kingdoms (W.H. Freeman, 1998), struggled heroically to justify the Protista (they preferred the term Protoctista) kingdom.  "Undulipodia (aka flagella) were present in common ancestors to all the phyla, even before mitochondria, given that the anaerobic archaeprotists bear them."  However, a sentence later they admit that "in some phyla, all members bear undulipodia, in other phyla, they are absent..."  It seems a shaky foundation on which to build a kingdom.  All human cells are fathered ultimately by sperm, which bear undulipodia, but no one has suggested that humans are therefore protists.

The answer is the option c. fact. Indeed facts are the events such as they occur, without interpretations or opinions. Facts happens and they can be observed by different means: you can get them through sense organs (eye, ear, mouth, skin, nose) or with instruments. When you report facts you must clearly state them appart of your interpretation or opinion.