Protista is a kingdom in which single-celled eukaryotic organisms are present. Protists don't have well-defined cell boundaries due to the presence of the nucleus. They form a link in different categories. The cell body of Protista contains a well-defined nucleus and membrane-bound organelles. Along with that some have cilia and some have flagella are also present that help in movement. Protist reproduces asexually as well as sexually depending on the external environment. So they show similarity with Plantae, fungi, and Animalia because they all are also eukaryotes. So the correct answer is D.