Concept:Ciliophora is a group of single-celled organisms that have cilia and are classified under the phylum Protozoa.Explanation:Ciliophora includes ciliates like Paramecium. These are considered the most complex protozoans. They have cilia at some life stage and two types of nuclei (macronucleus and micronucleus). They reproduce by binary fission. The other options are incorrect because Sipuncula belongs to phylum Annelida, Rotifers are a separate phylum Rotifera, and Echinoderms are phylum Echinodermata. Only Protozoa contains Ciliophora as a subphylum.Answer:B. Protozoa